Chapter 45

Lighting Systems

Learning Objectives

After reading this chapter, you will be able to:

• 45-01 Describe the purpose of the lighting system.
• 45-02 Describe the types of lights.
• 45-03 Describe light bulb configurations.
• 45-04 Describe park, tail, marker, and license lights.
• 45-05 Describe driving, fog, and cornering lights.
• 45-06 Describe brake and backup lights.
• 45-07 Describe turn signal and hazard lights.
• 45-08 Describe headlights and head light systems.
• 45-09 Describe lighting system testing and precautions.
• 45-10 Perform peripheral lighting service.
• 45-11 Perform headlight service.

ASE Education Foundation Tasks

The following ASE Education Foundation Automobile Accreditation Tasks are covered in this chapter:

• VIE1 Inspect interior and exterior lamps and sockets including headlights and auxiliary lights (fog lights/driving lights); replace as needed.
• VIE2 Aim headlights.
• VIE3 Identify system voltage and safety precautions associated with high-intensity discharge headlights.

Readings and Preparation

• Review all instructional materials, including the chapter in Fundamentals of Automotive Maintenance and Light Repair, Second Edition, and all related presentation support materials.

Support Materials

• Lecture PowerPoint presentation, including all Skill Drills

Pre-Lecture

• You Are the Automotive Technician
  • A progressive case study that encourages critical thinking skills.
  • Direct students to read the “You Are the Automotive Technician” scenario found at the beginning of each chapter.
  • Group Activity: Direct students to review the discussion questions at the end of the scenario and prepare a response to each question. Facilitate a class discussion centered on the questions.
  • Homework Assignment: Ask students to turn in their comments on the questions.
• Teaching Tip: Explain to students how this material applies to the workplace. Provide an example of a situation to make it relevant and meaningful. How does it fit into the broader picture? Is it building on something they already know? Will it help them master a skill? Students need to understand that what we are teaching is of importance on the job. This can be done by describing interesting lighting system problems you have experienced. You can also have students complete the online pre-test for this chapter in the CDX online system. This will help them understand what they do and do not know about lighting systems.

Lecture

45-01 Describe the purpose of the lighting system.

• Lighting systems improve the driver’s visibility at night and make a vehicle visible to others on the road.
• The headlight switch activates taillights, park lights, and headlights, which allows the driver to see the road ahead.
• A beam selector switch allows the driver to change the beams from high to low, or vice versa.
• Brake lights operate when the brake pedal is depressed.
• Red or amber turn signals alert other drivers of a change in direction.

45-02 Describe the types of lights.

• Different types of lamps used in modern vehicles include standard incandescent lamps, halogen lamps, vacuum tube fluorescent (VTF) lighting, HID xenon gas systems, LEDs, and more.
• Incandescent lamps consist of one or more tungsten filaments.
• Halogen lamps are another type of incandescent lamp.
• Light-emitting diodes (LEDs) turn on instantly and are particularly useful in brake lights.
• Vacuum tube fluorescent (VTF) lighting is used for instrumentation displays on instrument panel clusters.
• High-intensity discharge (HID) headlamps produce light with an electric arc; they typically produce between 2800 and 3500 lumens of light.

45-03 Describe light bulb configurations.

• All lamps or lightbulbs have letters and numbers on them that typically indicate the part number, operating voltage, and power consumed.
• Lamps and lightbulbs come in a variety of configurations to fit the various applications within a vehicle.
• One distinguishing feature is the number of filaments within a bulb. Single-filament bulbs are commonly used in courtesy lights, dash lights, and warning lights, whereas dual-filament bulbs have two filaments of different wattage.
• Another feature that differs among lights is the type of base on the lamp or the type of socket it fits into.

45-04 Describe park, tail, marker, and license lights.

• Park, tail, and marker lights are all low-intensity or low-wattage bulbs used to mark the outline or width of the vehicle (RC).
• Park lamps are placed at the front of the vehicle and are used at night when the vehicle is parked on the side of the road.
• Park lamps are yellow or white in color.
• Tail lamps are red and are located at the rear of the vehicle.
• Government regulations control the height of the lamps and their brightness.
• Marker lights are used to mark the sides of some vehicles.
• Red marker lamps face toward the rear, and yellow marker lamps face toward the front of the vehicle.
• License plate lamps produce a white light and are designed to illuminate the lettering on the license plate at night.

45-05 Describe driving, fog, and cornering lights.

• Driving lights provide high-intensity light over a long distance.
• Vehicle regulations specify the positioning and lens configuration of driving lights.
• Driving lights come in different sizes, shapes, lens patterns, and bulb wattage.
• Fog lights are used with other vehicle lighting in poor weather such as thick fog, driving rain, or blowing snow.
• Most older fog lights have yellow-colored reflectors; however, more recently, white fog lights have become more widely used.
• Cornering lights are white lights usually installed into the bumper or fender and are designed to provide side lighting when the vehicle is turning corners.
• Cornering lights turn on only when the headlights and turn signal switches are both on and turn off automatically when the turn signal cancels.

45-06 Describe brake and backup lights.

• Brake lights or stop lights are red lights mounted to the rear of the vehicle and are incorporated in the taillight cluster.
• Many vehicles, by law, now have a higher additional third brake light mounted on top of the trunk lid or near the rear window, called the center high mount stop light (CHMSL), or “chimsul”.
• The brake lights are activated whenever the driver operates the foot brake or when a control module automatically applies the brakes.
• The backup lights, also called reverse lights, are white lights mounted at the rear of a vehicle; they assist the driver with vision behind the vehicle at night.

45-07 Describe turn signal and hazard lights.

• Turn signal lights are located on the extreme corners of the vehicle and are usually amber in the front and can be either red or amber in the rear.
• A column-mounted switch, operated by the driver, directs a pulsing current to the turn signal lights on one side of the vehicle or the other.
• Turn signal lights warn other road users of the driver’s intended change of direction.
• The circuit for hazard warning lights connects into the turn signal lights and pulses all exterior turn signal lights and both indicator lights on the instrument panel.

45-08 Describe headlights and head light systems.

• Headlights are built into the front of a vehicle.
• They illuminate the road ahead of the vehicle when driving at night or in conditions of reduced visibility.
• In headlights, most vehicles require both a high beam and a low beam.
• High beam and a low beam, created by separate filaments, must be positioned correctly in relation to the highly polished reflector.
• The high-beam filament is precisely positioned; it projects the maximum amount of light forward and parallel to the road.
• The low-beam filament is often placed above and slightly to one side of the high-beam filament; this produces a beam of light that is projected slightly downward and toward the curb.
• A beam selector switch, typically located on the steering column, selects between low beam and high beam.
• A sealed-beam headlight has a highly polished aluminized glass reflector that is fused to the optically designed lens; it is a completely sealed unit that has the filaments accurately positioned in relation to the reflector.
• A semi-sealed beam headlight uses a replaceable bulb with a prefocus collar that locates the bulb in the headlight housing and controls the correct positioning of the filaments to the reflector and lens.
• An alternative to a reflector-type lighting system is a projection-type headlight system, which has a smaller front lens but produces a high-intensity forward beam; it uses a lens system, rather than the traditional reflector system, to project the light forward.
• Daytime running lights (DRLs) are an additional safety feature designed to improve the vehicle’s visibility to other drivers; they use existing lights that turn on when the vehicle is running and turn off when the engine stops.

45-09 Describe lighting system testing and precautions.

• The layouts of electrical circuits and their components are shown as diagrams.
• Being able to read a wiring diagram is probably the most important skill when diagnosing an electrical fault.
• Several safety precautions should be taken when working on HID systems.
• There is a risk of electrocution, burns, or shock from the high voltages generated by the HID system.
• Wear safety glasses, high-voltage safety gloves, and safety boots when working on HID systems.
• Persons with active electronic implants, such as heart pacemakers, should not work on HID headlamps.
• Dispose of the bulbs in HID headlamps in an environmentally friendly way.

45-10 Perform peripheral lighting service.

• When checking lighting and peripheral systems, be sure to work in a systematic manner to avoid missing a faulty bulb or other component.
• A vehicle may have warning lights that activate only if that circuit is in use.
• Inspecting the lighting system’s operation periodically will help identify any lightbulb issues.
• Look carefully at the bulb you are replacing to make sure you do not try to force the bulb in the wrong way, and make sure you don’t replace a dual-filament bulb with a single-filament bulb or vice versa.

45-11 Perform headlight service.

• Always make sure you replace a bulb with one of exactly the same type.
• When replacing a halogen bulb, avoid touching it with your fingers.
• If you inadvertently touch the bulb, clean it with alcohol and a lint-free cloth; do not use gasoline or paraffin to clean the bulb.
• The principle of aiming headlights is the same in the majority of cases, but the legal rules can differ from region to region.
• If the headlights are too dim, one reason could be high resistance in the light circuit, which can be checked by measuring the voltage drop on both the power side of the bulb and the ground side.
• If the voltage drop is less than 0.5 volt on each side, suspect the lightbulb is wearing out.
• A light intensity meter can be used to measure the amount of light energy produced by a lamp.

Post-Lecture

This section contains various student-centered end-of-chapter activities designed as enhancements to the instructor’s presentation. As time permits, these activities may be presented in class. They are also designed to be used as homework activities.

1. Direct students to read and individually answer the question sets located in the Wrap-Up section at the end of each chapter. Allow approximately 10–20 minutes for this part of the activity.
2. Facilitate a class review and discussion of the answers, allowing students to correct responses as may be needed. Use the answers noted in the Answer Key to assist in building this review.
3. You may wish to ask students to complete this activity on their own and turn in their answers on a separate piece of paper.

Review Questions

This question set is designed to assist students in understanding the chapter content by asking knowledge-based comprehension questions.

1. __________ headlamps produce light with an electric arc rather than a glowing filament.
   1. Vacuum tube fluorescent
   2. High-intensity discharge
   3. Incandescent and halogen
   4. Light-emitting diode

2. All of the following turn on with the taillights, EXCEPT:
   1. backup lights.
   2. license plate lights.
   3. park lights.
   4. side markers.

3. Which of the following is NOT a part of the reverse light circuit?
   1. Brake light switch
   2. Reverse light switch
   3. Ignition switch
   4. Vehicle battery

4. Red or amber turn signals alert other drivers of a change in direction and are mounted so they can always be seen from the __________ of the automobile.
   1. front
   2. rear
   3. sides
   4. All of these

5. Many vehicles use halogen light bulbs. What must you avoid when handling halogen bulbs?
   1. Touching the glass
   2. Touching the metal
   3. Touching the halogen gas
   4. Touching the terminal

6. Which lights are wired in parallel with the taillights and operate whenever the taillights are switched on?
   1. Headlights
   2. Turn signal lights
   3. Backup lights
   4. License plate lights

7. All of the following statements with respect to the function of headlights are true, EXCEPT:
   1. They illuminate the road ahead.
   2. They help drivers at the time of reduced visibility.
   3. They provide two beams, high and low, to serve different purposes.
   4. They are connected in series with each other.

8. When aiming headlights:
   1. make sure the wheels are pointed 20 degrees to the right.
   2. make sure the vehicle ride height is correct.
   3. adjust the tire pressure after aligning the headlights.
   4. place 100 pounds of weight in the trunk.

9. Which of the following lamps produce more lumens with a bluish tinge for the given wattage when compared with all other lamps?
   1. Incandescent lamps
   2. Halogen lamps
   3. High-intensity discharge lamps
   4. VTF lamps

10. Which type of light bulb has a base on each end of a cylindrical bulb?
    1. Bayonet style
    2. Festoon style
    3. Wedge style
    4. Dual-filament style

ASE Technician A/Technician B Style Questions

This question set is designed to assist students in gaining a further understanding of and familiarity with ASE Technician A/Technician B questions.

1. Technician A says light-emitting diodes (LEDs) have better visibility in inclement weather, operate at cooler tempera­tures, consume less energy, are much smaller, and can last up to 100 times longer than traditional bulbs. Technician B says LEDs can reduce the braking light response time by two-tenths of a second. Who is correct?
   1. Technician A
   2. Technician B
   3. Both A and B
   4. Neither A nor B

2. Two technicians are discussing brake light bulbs. Technician A says that a two-filament bulb uses the second filament as a back-up if the first filament burns out. Technician B says that two-filament bulbs have different wattage filaments. Who is correct?
   1. Technician A
   2. Technician B
   3. Both A and B
   4. Neither A nor B

3. Technician A says that all modern vehicles by law must be equipped with a center high mount stop lamp (CHMSL). Technician B says the CHMSL is usually mounted on top of the trunk lid or in the rear window of a vehicle. Who is correct?
   1. Technician A
   2. Technician B
   3. Both A and B
   4. Neither A nor B

4. Technician A says hazard warning lights use a flasher unit that can be a separate unit or the same as that used for the turn signals. Technician B says daytime running lights are used to warn other road users that a hazardous condition exists or that the vehicle is standing or parked in a danger­ous position on the side of the road. Who is correct?
   1. Technician A
   2. Technician B
   3. Both A and B
   4. Neither A nor B

5. Technician A says high-intensity discharge (HID) head­lamps produce light with an electric arc rather than a glow­ing filament. Technician B says HID lamps are commonly called xenon headlamps. Who is correct?
   1. Technician A
   2. Technician B
   3. Both A and B
   4. Neither A nor B

6. Technician A says park, tail, and marker lights are all high-intensity or high-wattage bulbs. Technician B says license plate illumination lamps are connected in series with the taillights. Who is correct?
   1. Technician A
   2. Technician B
   3. Both A and B
   4. Neither A nor B

7. Technician A says cornering lights are typically used in poor weather such as thick fog, driving rain, or blowing snow. Technician B says fog lights are red lights usually installed into the bumper or fender and are designed to provide side lighting when the vehicle is turning. Who is correct?
   1. Technician A
   2. Technician B
   3. Both A and B
   4. Neither A nor B

8. Technician A says that some brake lights get power from the brake switch through the turn signal switch. Technician B says many turn signals use amber lights. Who is correct?
   1. Technician A
   2. Technician B
   3. Both A and B
   4. Neither A nor B

9. Technician A says that incandescent bulbs resist vibration well. Technician B says that HID headlamps require a ballast to raise the voltage for the light. Who is correct?
   1. Technician A
   2. Technician B
   3. Both A and B
   4. Neither A nor B

10. Technician A says that a light intensity meter is used to measure the brightness of headlights. Technician B says that if a bulb is dim, you should perform a voltage drop test on the power and ground side of the bulb. Who is correct?
    1. Technician A
    2. Technician B
    3. Both A and B
    4. Neither A nor B

Assignments

• Review all materials from this chapter and be prepared for a chapter quiz to be administered (date to be determined by instructor).
• Direct students to read the next chapter in Fundamentals of Automotive Maintenance and Light Repair, Second Edition as listed on your syllabus to prepare for the next class session.

Chapter 44

Starting and Charging Systems

Learning Objectives

After reading this chapter, you will be able to:

• 44-01 Describe starting system fundamentals.
• 44-02 Describe starter motor construction.
• 44-03 Describe starter motor engagement.
• 44-04 Describe armature windings and commutators.
• 44-05 Describe starter drives and the ring gear.
• 44-06 Describe solenoid operation.
• 44-07 Describe starter control circuit operation.
• 44-08 Test starter high-current draw.
• 44-09 Test starter control circuit voltage drop.
• 44-10 Test starter relays and solenoids.
• 44-11 Remove and install a starter.
• 44-12 Describe idle–stop/start–stop system operation.
• 44-13 Describe charging system operation.
• 44-14 Describe the rotor, slip ring, and brushes.
• 44-15 Describe the stator, end frames, fan, and pulley.
• 44-16 Describe rectification.
• 44-17 Describe voltage regulation.
• 44-18 Perform a charging system output test.
• 44-19 Perform charging system circuit voltage and voltage drop tests.
• 44-20 Replace alternator.

ASE Education Foundation Tasks

The following ASE Education Foundation Automobile Accreditation Tasks are covered in this chapter:

• VIC1 Perform starter current draw test; determine necessary action.
• VIC2 Perform starter circuit voltage drop tests; determine necessary action.
• VIC3 Inspect and test starter relays and solenoids; determine necessary action.
• VIC4 Remove and install starter in a vehicle.
• VIC5 Inspect and test switches, connectors, and wires of starter control circuits; determine necessary action.
• VIC6 Demonstrate knowledge of an automatic idle-stop/start-stop system.
• VID1 Perform charging system output test; determine necessary action.
• VID3 Remove, inspect, and/or replace generator (alternator).
• VID4 Perform charging circuit voltage drop tests; determine necessary action.

Readings and Preparation

• Review all instructional materials, including the chapter in Fundamentals of Automotive Maintenance and Light Repair, Second Edition, and all related presentation support materials.

Support Materials

• Lecture PowerPoint presentation, including all Skill Drills

Pre-Lecture

• You Are the Automotive Technician
  • A progressive case study that encourages critical thinking skills.
  • Direct students to read the “You Are the Automotive Technician” scenario found at the beginning of each chapter.
  • Group Activity: Direct students to review the discussion questions at the end of the scenario and prepare a response to each question. Facilitate a class discussion centered on the questions.
  • Homework Assignment: Ask students to turn in their comments on the questions.
• Teaching Tip: Explain to students how this material applies to the workplace. Provide an example of a situation to make it relevant and meaningful. How does it fit into the broader picture? Is it building on something they already know? Will it help them master a skill? Students need to understand that what we are teaching is of importance on the job. This can be done by describing interesting starting and charging system problems you have experienced. You can also have students complete the online pre-test for this chapter in the CDX online system. This will help them understand what they do and do not know about starting and charging systems.

Lecture

44-01 Describe starting system fundamentals.

• The starting system provides a method of rotating (cranking) the vehicle’s internal combustion engine (ICE) so that the combustion cycle can begin.
• Modern vehicles use an electric starter motor that draws its electrical power from the vehicle’s battery.
• The starting/cranking system consists of two electrical circuits: the high-amperage circuit that powers the starter for cranking the engine over and the low-amperage circuit used to control the high-amperage circuit.
• The high-amperage circuit consists of battery, high-amperage side of the solenoid, and starter motor assembly.
• The control circuit consists of the battery, ignition switch, safety switch (clutch switch or neutral safety switch), and the low-amperage side of the solenoid.
• The starter motor converts electrical energy to mechanical energy for the purpose of cranking the engine over.
• There are three sections to the typical starter: the electric motor, the drive mechanism, and the solenoid battery.
• Starters can be either direct-drive (where the starter drive is mounted directly on one end of the armature shaft) or gear reduction (which use an extra gear between the armature and the starter drive mechanism).

44-02 Describe starter motor construction.

• A starter motor normally consists of the following components: field coils or large permanent magnets, an armature, a commutator, brushes, a drive pinion with an overrunning clutch, and a drive pinion engagement solenoid and shift fork batteries.
• The armature is the revolving component of the DC motor; the armature shaft is supported at each end by bushings or bearings pressed into end frames.
• The commutator end frame carries copper-impregnated carbon brushes that conduct current through the armature when it is being rotated in operation.
• The brushes are mounted in brush holders and are kept in contact with the commutator by tensioned spiral springs.
• Starter motors use two magnet types: electromagnetic and permanent magnet.
• Electromagnetic fields are created as current flows through heavy copper windings wound around iron pole shoes to concentrate the magnetic field.
• The pole shoes are fastened to the starter case/barrel.
• Permanent magnets are located similarly but they do not need electricity and therefore occupy less space.

44-03 Describe starter motor engagement.

• Engagement is initiated by operation of the ignition switch, which activates a starter-mounted solenoid.
• The solenoid plunger attached to a pinion shift lever and operating fork is moved by solenoid operation, causing the pinion to engage with the ring gear and the plunger contacts to bridge the main starter terminals.

44-04 Describe armature windings and commutators.

• A conductor loop that can freely rotate within the magnetic field is the most efficient motor design.
• When current flows through the loop, the stationary magnetic field is distorted and the lines of force try to straighten, forcing one side of the loop up and the other side of the loop down, and causing the loop to rotate until it is at 90 degrees to the magnetic field.
• To continue rotation, the direction of current flow in the conductor must be reversed at this static neutral point.
• A commutator is used to continually reverse the current flow in the loop, which keeps the armature rotating.

44-05 Describe starter drives and the ring gear.

• The starter drive transmits the rotational drive from the starter armature to the engine via the ring gear mounted on the engine flywheel, flexplate, or torque converter.
• The starter drive is composed of a pinion gear, an internal spline that mates with the slightly curved external spline on the armature shaft, an overrunning clutch, and a meshing spring.
• The pinion gear is small in comparison to the ring gear.
• The overrunning clutch drives the pinion gear in one direction while allowing it to freewheel in the opposite direction.
• The overrunning clutch prevents the starter motor from being driven by the engine once the engine starts.

44-06 Describe solenoid operation.

• The solenoid is typically a cylindrical device mounted on the starter motor constructed with two electrical windings, a pull-in winding, and a hold-in winding.
• Two main functions performed by solenoid are the following: it switches the high current flow required by the starter motor on and off and it engages the starter drive with the ring gear.

44-07 Describe starter control circuit operation.

• The starter control circuit provides a means of operating the starter motor only within certain parameters: when the transmission is in Park, the clutch is depressed, the brake pedal is applied, or the proper ignition key is being used.
• These requirements help prevent accidentally starting the vehicle in gear and also help prevent the vehicle from being stolen.
• When the required parameters are met, the PCM either activates a starter relay or activates the solenoid directly.
• Vehicle immobilizers are computer-managed security systems that disable the vehicle starter and engine systems by using an electronic system to uniquely identify each vehicle key by a security code system.
• Another type of immobilizer system uses a static code programmed into circuitry built into the key.
• Immobilizer systems now use keyless starting where the vehicle has a start button on the dash and does not require the key; the start button will start the vehicle only if the key is in the proximity of the vehicle.
• A further variation of keyless starting is where the vehicle can be started remotely (e.g., inside the house); a start button is located on the key fob.

44-08 Test starter high-current draw.

• Starter motors can be tested in two ways: on vehicle or off vehicle.
• The on-vehicle test is usually called a starter draw test and the off-vehicle test is called a starter no-load test.
• As the starter motor and engine cranking speed increase, the current draw decreases and quickly stabilizes once the engine reaches full cranking speed; it is at this point that the amperage is read and then compared with specifications.
• Starter test equipment used to test starter draw uses an inductive high-current ammeter to measure the cranking current flow.

44-09 Test starter control circuit voltage drop.

• Voltage drop can occur across both the high-current and control circuits; however, the high-current circuit is more susceptible to voltage drop.
• When testing the voltage drop on the high-current side, for the measurement to be meaningful, the starter must be activated.
• A digital multimeter (DMM) is used to measure voltage drop across all parts of the circuit.
• A voltmeter with a minimum/maximum range setting is very useful when measuring voltage drop.
• Voltage drop is tested while the circuit is under load.
• The starter control circuit activates the starter solenoid, which activates the starter motor.
• If there is a problem in the starter control circuit, the vehicle will likely not crank over at all, or maybe intermittently.
• The control circuit is made up of the battery, fusible link, ignition switch, neutral safety switch (automatic transmission vehicles), clutch switch (manual transmission vehicles), starter relay, and solenoid windings.
• Start by placing the DMM’s black lead on the battery positive terminal, place the red lead on the solenoid’s input terminal (control circuit terminal), and measure the voltage drop with the key in the crank position.
• If the voltage drop is more than 0.5 volts, perform individual voltage drop tests on the power side of the control circuit.
• If the voltage drop is less than 0.5 volts, then measure the voltage drop on the starter ground circuit.

44-10 Test starter relays and solenoids.

• Relays must be tested in two or three ways depending on the relay.
• The simplest test is to measure the resistance of the relay winding; if it is out of specifications, the relay will need to be replaced; if it is OK, the contacts will need to be tested for an excessive voltage drop.
• Solenoids can be difficult to test on the vehicle due to poor access; the tests will usually be limited to voltage and voltage drop tests on the main contacts.
• It is usually best to disconnect the control circuit connector from the solenoid.
• Use a jumper wire to apply battery voltage to the control circuit terminal on the solenoid; if the solenoid clicks, then there is likely a fault in the control circuit wiring; if it does NOT click, then the solenoid windings are open, or the starter brushes are likely worn.

44-11 Remove and install a starter.

• Starter motors are usually located close to the flywheel end of the engine.
• They can be in difficult-to-reach locations.
• Some engine components or covers may need to be removed to gain access.
• In most cases, the starter can be accessed more easily from underneath the vehicle.

44-12 Describe idle–stop/start–stop system operation.

• This system automatically shuts the engine off at times, typically when the vehicle is stopped, and then restarts the engine when needed.
• Some vehicles use a flywheel-mounted motor/generator or geared motor generator to start the engine quickly.
• The second type uses an upgraded starter motor, which can turn the engine over faster than normal.
• The third type of system is unique because it does not rely solely on a starter motor; instead, it ignites a combustible mixture in an appropriate cylinder.

44-13 Describe charging system operation.

• DC generators have not been used on most vehicles since the 1960s; alternators have taken over.
• Both DC generators and alternators produce electricity by relative movement between conductors and a magnetic field which induces an electrical potential or voltage within the conductors.
• Alternators or AC generators create the needed electrical energy whenever the engine is operating.
• The main parts of the charging system include the battery, alternator, voltage regulator (internal or external), charge warning light, and wiring that completes the circuit.
• The battery stores electrical energy in chemical form.
• The battery acts as an electrical dampening device and also provides the electrical energy for cranking the engine.
• Once the engine is running, the alternator converts some of the engine’s mechanical energy into electrical energy, which is used to operate all the electrical components on the vehicle.
• The alternator also charges the battery to replace the energy used to start the engine.
• The voltage regulator circuit maintains optimal battery state of charge.
• The alternator converts mechanical energy into electrical energy by electromagnetic induction.
• The value of the electromotive force (EMF) or voltage potential induced by an AC generator depends on four factors relating to the strength of the magnetic field. Increasing the strength of the magnetic field increases the value of the induced EMF, the speed at which the magnet rotates, the relative distance between the magnet and conductors, and the number of turns of wire on the stationary coil.

44-14 Describe the rotor, slip ring, and brushes.

• The alternator consists of a stationary winding assembly called the stator, a rotating electromagnet called the rotor, with a slip ring, a brush assembly, a rectifier assembly, two end frames, and a cooling fan and drive pulley engine.
• The rotor is an electromagnet that rotates freely in the alternator and is supported on each end by ball bearings.
• The rotor consists of a coil of insulated wire wound around an iron core and pressed onto a steel shaft.
• When current is passed through the slip rings and the coil winding, it establishes strong north and south poles at the ends of the iron core and the shaft.
• Slip rings and brushes aid in making an electrical connection to the rotating rotor assembly.
• Slip rings are normally copper bands that are molded onto an insulating material, and then pressed onto the steel shaft of the rotor.
• Each end of the rotor winding is connected to one of the copper bands.
• Brushes are made of a combination of copper and carbon and are carried in brush holders mounted in the end frame of the alternator.
• As the rotor rotates, the brushes maintain a constant connection with each end of the winding.
• Alternator brushes can wear out and cause breakdowns.
• Brushless alternators induce current flow into the rotor through one stationary field winding in the housing and a separate armature on the rotor.

44-15 Describe the stator, end frames, fan, and pulley.

• The stator consists of a cylindrical, laminated iron core; it carries the three- (or four-) phase windings in slots on the inside.
• The stator is mounted between the two end housings.
• The alternator housings are typically constructed from aluminum and have vents within the frames to provide for a large amount of airflow to assist in dissipating heat.
• The alternator’s cooling fan is a powerful centrifugal type of fan mounted on the rotor shaft and may be an integral part of the drive pulley or part of the rotor.
• Overrunning alternator pulley (OAP) is a new feature that has been added to alternators over the past number of years; another type is called an overrunning alternator decoupler (OAD) or alternator decoupling pulleys (ADPs).
• The following functions are provided by ADPs: reduce belt noise and vibration, reduce stress placed on the tensioner and belt, extend belt and tensioner life, and improve fuel economy.

44-16 Describe rectification.

• Rectification is a process of converting AC into DC.
• DC is required by the battery and nearly all of the automobile systems.
• To change AC to DC, automotive alternators use a rectifier assembly, which consists of diodes in a specific configuration.
• A diode allows current to flow in one direction but blocks the flow of current in the other direction.
• A three-phase “bridge” rectifier has a minimum of six diodes (three positive and three negative); it rectifies the AC output of the stator windings to DC.

44-17 Describe voltage regulation.

• The voltage regulator monitors battery voltage; it adjusts the current flowing through the rotor appropriately.
• When voltage output is low, the regulator allows more current to flow through the rotor field winding, which increases the strength of the magnetic field and alternator output.
• As the output voltage increases to the maximum regulated voltage, the voltage regulator reduces the current flow through the rotor, which reduces the strength of the magnetic field and alternator output.
• In an A-type regulating circuit, alternator B+ output is fed directly to the rotor, and voltage regulation is done on the ground side of the field.
• In a B-type circuit, the voltage regulator is on the positive side of the rotor field, and the ground is constant.
• The voltage regulator in modern vehicles is a solid-state electronic device with an electronic circuit that senses the battery voltage and switches the rotor circuit on and off rapidly.

44-18 Perform a charging system output test.

• The testing of an alternator output initially involves testing the system’s regulated voltage using a voltmeter.
• Regulated voltage should be between the manufacturer’s specified minimum and maximum regulated voltage.
• Once the regulated voltage is confirmed, the charging system output is checked by using an external electrical load.
• A carbon pile is commonly used to reduce the battery voltage, which tricks the regulator into full-fielding the alternator, making it produce maximum output.
• The output is read using an inductive ammeter and compared with the manufacturer’s rated output specifications.

44-19 Perform charging system circuit voltage and voltage drop tests.

• A DMM is used to measure voltage drop across all parts of the charging system circuit.
• Voltage drop tests are valid only when the circuit is under load.
• To measure for voltage drop across charging system circuit, the DMM is connected in parallel across the component, cable, or connection that is to be tested.

44-20 Replace alternator.

• Alternators have to be replaced whenever they are electrically or mechanically faulty.
• Electrical faults include no-charge, undercharge, or overcharge conditions.
• Mechanical faults include worn bearings or other internal or external mechanical damage.
• When replacing an alternator, the negative terminal of the battery should be disconnected.

Post-Lecture

This section contains various student-centered end-of-chapter activities designed as enhancements to the instructor’s presentation. As time permits, these activities may be presented in class. They are also designed to be used as homework activities.

1. Direct students to read and individually answer the question sets located in the Wrap-Up section at the end of each chapter. Allow approximately 10–20 minutes for this part of the activity.
2. Facilitate a class review and discussion of the answers, allowing students to correct responses as may be needed. Use the answers noted in the Answer Key to assist in building this review.
3. You may wish to ask students to complete this activity on their own and turn in their answers on a separate piece of paper.

Review Questions

This question set is designed to assist students in understanding the chapter content by asking knowledge-based comprehension questions.

1. Which of the following is part of the starter control circuit?
   1. The high-amperage side of the solenoid
   2. The starter motor assembly
   3. The ignition switch
   4. The flywheel

2. Starter motor magnet types are typically permanent magnet and:
   2. semi-permanent magnet.
   3. temporary magnet.
   4. part-time magnet.

3. Which part of the starter assembly is responsible for moving the drive pinion gear into engagement with the ring gear?
   1. The electric motor
   2. The solenoid plunger
   3. The armature windings
   4. The one-way clutch

4. Which of the following is true when performing a starter draw test?
   1. The engine should be allowed to start up during the test.
   2. The starter should be off-vehicle and placed in a test stand.
   3. The engine should be disabled so it will crank but not start.
   4. The spark plugs should be removed from the engine.

5. All of the following are ways to test a starter relay, EXCEPT:
   1. Measure resistance of the coil windings.
   2. Check voltage drop across the contacts.
   3. Use a 9 V battery on the winding terminals.
   4. Reverse the relay position in the fuse box.

6. How should a technician prevent sparks or short circuits when replacing a starter?
   1. Disconnect the negative battery terminal.
   2. Remove the starter fuse.
   3. Remove the starter relay.
   4. Take the key out of the ignition.

7. Which charging system component is responsible for maintaining the optimal battery state of charge?
   1. The stator windings
   2. The charge warning light
   3. The voltage regulator
   4. The slip rings and brushes

8. Which component is an electromagnet that rotates freely inside an alternator?
   1. The brush assembly
   2. The slip ring
   3. The rectifier
   4. The rotor

9. If a technician uses a screwdriver to short out the shorting tab on the back of an alternator, what should happen?
   1. The circuit breaker should trip to protect the circuit.
   2. The alternator should charge at full output.
   3. The engine should stall out and not restart.
   4. The charging light should turn on in the instrument panel.

10. Which of the following is most likely to cause an overcharging condition?
    1. A loose or slipping drive belt
    2. Worn brushes in the alternator
    3. Voltage drop in the alternator output circuit
    4. A faulty voltage regulator

ASE Technician A/Technician B Style Questions

This question set is designed to assist students in gaining a further understanding of and familiarity with ASE Technician A/Technician B questions.

1. A starter motor is being discussed. Technician A states that if a conductor is placed so it cuts across a magnetic field, the conductor will be forced out of the magnetic field. Techni­cian B states that the commutator reverses the current flow through the armature as it spins. Who is correct?
   1. Technician A
   2. Technician B
   3. Both A and B
   4. Neither A nor B

2. A starter solenoid is being discussed. Technician A states that the starter solenoid switches the high current flow to the starter motor on and off. Technician B states that the solenoid is controlled by the PCM on some vehicles. Who is correct?
   1. Technician A
   2. Technician B
   3. Both A and B
   4. Neither A nor B

3. A starter control circuit is being discussed. Technician A states that the neutral safety switch is used to prevent the engine from being started in gear. Technician B states that automatic transmission equipped vehicles use a clutch pedal switch as part of the starter control circuit. Who is correct?
   1. Technician A
   2. Technician B
   3. Both A and B
   4. Neither A nor B

4. Testing high current starter circuit voltage drop is being discussed. Technician A states that the battery should be disconnected for this test. Technician B states that typically the starter cable should not drop more than 0.5 volts during cranking. Who is correct?
   1. Technician A
   2. Technician B
   3. Both A and B
   4. Neither A nor B

5. Testing the starter control circuit is being discussed. Techni­cian A states that the voltage tests on the circuit should be performed with the key in the crank position. Technician B states that a problem in the starter control circuit often causes the starter to crank slowly. Who is correct?
   1. Technician A
   2. Technician B
   3. Both A and B
   4. Neither A nor B

6. The idle stop/start system is being discussed. Technician A states that the purpose of start/stop systems is to make the starter last longer. Technician B states that some start/stop systems don’t use a starter motor to crank the engine over. Who is correct?
   1. Technician A
   2. Technician B
   3. Both A and B
   4. Neither A nor B

7. An alternator is being discussed. Technician A states that the stator is the rotating part connected to the pulley. Tech­nician B states that some alternators have an overrunning pulley that can be turned on or off by the PCM. Who is correct?
   1. Technician A
   2. Technician B
   3. Both A and B
   4. Neither A nor B

8. Alternators are being discussed. Technician A states that the purpose of a rectifier is to convert AC to DC. Techni­cian B states that a rectifier consists of a total of three diodes. Who is correct?
   1. Technician A
   2. Technician B
   3. Both A and B
   4. Neither A nor B

9. A charging system output test is being performed. Technician A states that the alternator output involves measuring the system voltage with a volt meter. Techni­cian B states that a carbon pile tester can be used to trick the alternator into charging at full output. Who is correct?
   1. Technician A
   2. Technician B
   3. Both A and B
   4. Neither A nor B

10. An alternator is being replaced. Technician A states that the battery negative terminal must be disconnected to prevent a possible short circuit when removing the output terminal. Technician B states that belt tension needs to be checked as part of replacement. Who is correct?
    1. Technician A
    2. Technician B
    3. Both A and B
    4. Neither A nor B

Assignments

• Review all materials from this chapter and be prepared for a chapter quiz to be administered (date to be determined by instructor).
• Direct students to read the next chapter in Fundamentals of Automotive Maintenance and Light Repair, Second Edition as listed on your syllabus to prepare for the next class session.

Chapter 43

Battery Systems

Learning Objectives

After reading this chapter, you will be able to:

• 43-01 Describe basic battery construction and operation.
• 43-02 Describe basic types of batteries.
• 43-03 Describe battery configurations, terminals, and cables.
• 43-04 Describe battery ratings and the charge–discharge cycle.
• 43-05 Describe conditions that shorten/lengthen the life of a battery.
• 43-06 Describe the purpose and types of battery maintenance.
• 43-07 Inspect, clean, fill, and replace the battery and cables.
• 43-08 Perform battery charging and jump-starting.
• 43-09 Perform battery state of charge and specific gravity tests.
• 43-10 Perform battery capacity tests.
• 43-11 Maintain and restore electronic memories.
• 43-12 Measure parasitic draw.

ASE Education Foundation Tasks

The following ASE Education Foundation Automobile Accreditation Tasks are covered in this chapter:

• VIA8 Measure key-off battery drain (parasitic draw).
• VIB1 Perform battery state-of-charge test; determine necessary action.
• VIB2 Confirm proper battery capacity for vehicle application; perform battery capacity and load test; determine necessary action.
• VIB3 Maintain or restore electronic memory functions.
• VIB4 Inspect and clean battery; fill battery cells; check battery cables, connectors, clamps, and hold-downs.
• VIB5 Perform slow/fast battery charge according to manufacturer’s recommendations.
• VIB6 Jump-start vehicle using jumper cables and a booster battery or an auxiliary power supply.
• VIB8 Identify electrical/electronic modules, security systems, radios, and other accessories that require reinitialization or code entry after reconnecting vehicle battery.
• VIB9 Identify hybrid vehicle auxiliary (12v) battery service, repair, and test procedures.

Readings and Preparation

• Review all instructional materials, including the chapter in Fundamentals of Automotive Maintenance and Light Repair, Second Edition, and all related presentation support materials.

Support Materials

• Lecture PowerPoint presentation, including all Skill Drills

Pre-Lecture

• You Are the Automotive Technician
  • A progressive case study that encourages critical thinking skills.
  • Direct students to read the “You Are the Automotive Technician” scenario found at the beginning of each chapter.
  • Group Activity: Direct students to review the discussion questions at the end of the scenario and prepare a response to each question. Facilitate a class discussion centered on the questions.
  • Homework Assignment: Ask students to turn in their comments on the questions.
• Teaching Tip: Explain to students how this material applies to the workplace. Provide an example of a situation to make it relevant and meaningful. How does it fit into the broader picture? Is it building on something they already know? Will it help them master a skill? Students need to understand that what we are teaching is of importance on the job. This can be done by describing interesting battery problems you have experienced. You can also have students complete the online pre-test for this chapter in the CDX online system. This will help them understand what they do and do not know about battery systems.

Lecture

43-01 Describe basic battery construction and operation.

• A battery transforms electrical to chemical energy and vice versa.
• A battery consists of two dissimilar metals: an insulator material separating the metals and an electrolyte, which is an electrically conductive solution.
• The traditional automotive battery type is the lead-acid battery.
• The standard 12-volt car battery consists of six 2.1-volt cells connected in series, each containing two sets of electrodes or plates immersed in an electrolyte solution of diluted sulfuric acid (H₂SO₄) and water.
• The positive plates are assembled alternate to negative plates and parallel to other positive plates, and the negative plates are assembled alternate to positive plates and parallel to other negative plates.

43-02 Describe basic types of batteries.

• Deep-cycle batteries are made with heavier lead plates that tolerate deep discharging better than starting batteries.
• Deep-cycle batteries are heavier and bulkier than starting batteries and have a lower output per pound.
• Low-maintenance batteries require little, if any, topping off of the water in the electrolyte but still have removable caps.
• Absorbed glass mat batteries (suited for off-road and racing vehicles) have a gel electrolyte that is absorbed in a mat of fine glass fibers.
• Sealed or maintenance-free batteries typically have no removable cell covers; some of them have a visual indicator called a single-cell hydrometer float that provides information on the status of the charge and condition of one of the battery cells.
• Cell phones and tablet computers have rechargeable cell batteries that may be nickel-cadmium (Ni-Cd), nickel-metal hydride (Ni-MH), or lithium ion (Li-ion)
• A nickel-metal hydride battery can have two to three times the energy of nickel-cadmium batteries.
• A lithium-ion battery has one of the highest energy density ratios, meaning that it can store more energy than other comparable batteries, and it has a low self-discharge rate.
• In hybrid or electric vehicle applications, many small individual cells are connected in series to each other and in parallel to other series arrangements, forming a battery pack.
• Advantages of lithium-ion batteries include high energy density, low self-discharge, low maintenance, no periodic discharge requirement, no memory, and low internal resistance.
• Disadvantages of lithium-ion batteries include need for circuit protection, sensitivity to high temperatures, increased cost of manufacturing, and potential for damage if completely discharged.

43-03 Describe battery configurations, terminals, and cables.

• Physical attributes of the automotive battery include the size of the battery case, the location of the battery terminals, and the size or type of battery terminal.
• Battery cables and terminals are designed to carry high discharge currents and are usually made of solid lead or zinc-plated brass.
• Types of battery terminals are cone design, side terminal, and flat terminal; the most common is cone design.

43-04 Describe battery ratings and the charge–discharge cycle.

• The three most common methods used to rate automotive battery capacity are cold cranking amps (CCAs), cranking amps (CAs), and reserve capacity (RC).
• CCA measures the load in amps that a battery can deliver for 30 seconds while maintaining a voltage of 1.2 volts per cell or higher at 0°F (-17.8°C).
• CA measures the same thing, but at a higher temperature of 32°F (0°C).
• RC is the time in minutes that a new, fully-charged battery at 80°F (26.7°C) will supply a constant load of 25 amps without its voltage dropping below 10.5 volts for a 12-volt battery.
• The RC rating approximates the amount of time a vehicle can be driven before the battery dies if the charging system fails completely.
• As the battery creates current flow to operate electrical devices, it is being discharged.
• As it discharges, the sulfuric acid in the electrolyte joins with lead dioxide to form lead sulfate, and the oxygen from the plate joins the hydrogen from the electrolyte to form water.
• When being charged, electrical pressure (voltage) is higher than that of the battery’s total cell voltage, which pushes electricity back into the battery, reversing the chemical process.

43-05 Describe conditions that shorten/lengthen the life of a battery.

• Conditions that shorten a battery’s life include being fully discharged or having deep discharge cycles, remaining overcharged or undercharged, experiencing high discharge rates for extended periods, experiencing excessive vibration, being exposed to extremes of temperature, having dirt or moisture on the case, and developing corrosion.
• Batteries should be kept clean, dry, and fully charged.

43-06 Describe the purpose and types of battery maintenance.

• Regular maintenance of batteries includes inspection, cleaning, testing, and charging when discharged.

43-07 Inspect, clean, fill, and replace the battery and cables.

• Maintenance tasks such as inspecting, cleaning, and filling batteries should be performed every six months to one year on top-post batteries and every 1–2 years on side-post batteries.

43-08 Perform battery charging and jump-starting.

• Slow charging is less stressful on a battery than fast charging.
• To determine the ideal charging rate: CCAs divided by 70.
• To determine the max charging rate: CCAs divided by 40.
• Never exceed 15.5 volts when charging a 12-volt flooded cell battery, 14.8 volts when charging a 12-volt AGM battery, and 14.3 volts when charging a 12-volt gel cell battery.
• Jump-starting a vehicle is the process of using one vehicle to start another vehicle; the vehicle with a charged battery provides electrical energy to start the vehicle that has a discharged battery.
• Some vehicles should NOT be jump started.

43-09 Perform battery state of charge and specific gravity tests.

• There are two tests for determining the battery’s state of charge: the specific gravity test and the open circuit voltage test.
• The specific gravity test measures the electrolyte’s specific gravity; it indicates the acid content, and so the state of charge.
• The open circuit voltage test uses a DMM to accurately measure the voltage of a battery and is a very quick and reasonably accurate indicator of battery state of charge.

43-10 Perform battery capacity tests.

• The conductance tester can determine a battery’s CCA capacity by measuring its conductance.
• The conductance tester sends low-frequency signals into the battery, which allows it to determine the battery’s ability to conduct current.
• The load test is used to test a battery’s capacity and internal condition.
• The load test subjects the battery to a high rate of discharge, and the voltage is then measured at the end of a set time to see how well the battery creates that current flow.

43-11 Maintain and restore electronic memories.

• Many electronic modules in vehicles require a small amount of power to maintain their keep alive memory (KAM).
• When the battery is disconnected, memory is usually lost.
• Loss of memory may prevent the vehicle from being restarted or the radio from being used.
• In some cases, it may be possible to use a memory saver to maintain the vehicle’s memory while the battery is disconnected.
• Many technicians use an external 12-volt DC power supply connected to the data link connector with a suitable cable.

43-12 Measure parasitic draw.

• All modern vehicles have a small amount of current draw when the ignition is turned off, which is called parasitic draw.
• The total parasitic draw should be a relatively small amount of current because excessive parasitic draw will discharge the battery over a short amount of time.
• The most common way of measuring parasitic draw is by using an ammeter capable of measuring milliamps.
• The ammeter is inserted in series between one of the battery posts and the battery terminal.
• The Chesney parasitic load test uses an ohmmeter to indicate the size of the parasitic draw.

Post-Lecture

This section contains various student-centered end-of-chapter activities designed as enhancements to the instructor’s presentation. As time permits, these activities may be presented in class. They are also designed to be used as homework activities.

1. Direct students to read and individually answer the question sets located in the Wrap-Up section at the end of each chapter. Allow approximately 10–20 minutes for this part of the activity.
2. Facilitate a class review and discussion of the answers, allowing students to correct responses as may be needed. Use the answers noted in the Answer Key to assist in building this review.
3. You may wish to ask students to complete this activity on their own and turn in their answers on a separate piece of paper.

Review Questions

This question set is designed to assist students in understanding the chapter content by asking knowledge-based comprehension questions.

1. The electrolyte in an automotive lead acid battery is:
   1. dilute sulfuric acid.
   2. hydrochloric acid.
   3. sulfur dioxide.
   4. nitric acid.

2. Absorbed glass mat batteries have the electrolyte absorbed within a mat of fine glass fibers, and are a type of:
   1. low-maintenance battery.
   2. unsealed battery.
   3. maintenance-free battery.
   4. single-cell hydrometer battery.

3. The most common battery cable terminal is a __________ that provides a large surface contact area with the ability to tighten the terminal onto the battery post using a nut and bolt.
   1. side terminal design
   2. cone design
   3. flat terminal design
   4. back terminal design

4. CCA measures the load in amps that a battery can deliver for __________ while maintaining a voltage of __________ volts per cell.
   2. 60 seconds; 2.1
   3. 30 seconds; 2.1
   4. 60 seconds; 1.2
   5. 30 seconds; 1.2

5. Clean the battery with a mixture of __________, but make sure not to get any of that mixture down inside of the battery, as it will tend to neutralize the electrolyte, damaging the battery.
   1. baking soda and water
   2. soap and water
   3. salt and water
   4. alcohol and water

6. What is the correct sequence for disconnecting battery ter­minals?
   1. Disconnect the negative terminal and then the positive terminal
   2. Disconnect whichever terminal is the easiest first
   3. Disconnect whichever terminal is hardest first
   4. Disconnect the positive terminal and then the negative terminal

7. When a vehicle has been shut off, it can have a:
   1. thermal runaway.
   2. parasitic draw.
   3. paralysis draw.
   4. heat runaway.

8. When performing an open circuit voltage test to determine the battery state of charge, what should a fully charged battery read?
   12. 0 volts
   13. 2 volts
   14. 6 volts
   15. 5 volts

9. When performing a battery load test, what should the load be set to?
   1. 150 amps
   2. 300 amps
   3. Two times the cold cranking amps (CCA)
   4. Half the cold cranking amps (CCA)

10. When using a DMM to measure parasitic draw, connect the meter leads:
    1. between one of the battery posts and terminal on the battery cable.
    2. from one battery post to the other.
    3. from the positive battery post to a good engine ground.
    4. across the high current contacts on the starter solenoid.

ASE Technician A/Technician B Style Questions

This question set is designed to assist students in gaining a further understanding of and familiarity with ASE Technician A/Technician B questions.

1. Technician A says that a battery stores electrical energy in chemical form. Technician B says that the chemical reactions change the composition of the chemicals, which then are stored until the electrical energy is needed. Who is correct?
   1. Technician A
   2. Technician B
   3. Both A and B
   4. Neither A nor B

2. Technician A says that when disconnecting the battery, the negative terminal should be disconnected first. Technician B says that when disconnecting the battery terminals, always remove the positive terminal complete­ly first. Who is correct?
   1. Technician A
   2. Technician B
   3. Both A and B
   4. Neither A nor B

3. Two technicians are discussing the specific gravity test. Technician A says that if the electrolyte level is too low, then you will have to add distilled water, and the battery will have to be fully charged to mix the water and acid. Tech­nician B says that the battery should be topped up with a mixture of acid and water. Who is correct?
   1. Technician A
   2. Technician B
   3. Both A and B
   4. Neither A or B

4. Two technicians are discussing battery load testing. Tech­nician A says that if the battery fails the load test, it is bad and should be replaced. Technician B says if it fails the load test, it should be fully charged and the test repeated. Who is correct?
   1. Technician A
   2. Technician B
   3. Both A and B
   4. Neither A nor B

5. Two technicians are discussing measuring parasitic draw. Technician A says that the parasitic draw is measured with an ammeter. Technician B says that the parasitic draw is measured with a voltmeter. Who is correct?
   1. Technician A
   2. Technician B
   3. Both A and B
   4. Neither A nor B

6. Technician A says that batteries should be charged as fast as possible. Technician B says that the ideal charging rate is the CCA divided by 70. Who is correct?
   1. Technician A
   2. Technician B
   3. Both A and B
   4. Neither A nor B

7. Technician A says that lead oxide acts as an insulator on the battery posts and has to be scraped away. Technician B says that current can leak across the dirt on the surface of the battery. Who is correct?
   1. Technician A
   2. Technician B
   3. Both A and B
   4. Neither A nor B

8. Technician A says that checking the specific gravity will indicate the battery’s cold cranking amps. Technician B says that a battery load test should be performed when the battery is heavily discharged. Who is correct?
   1. Technician A
   2. Technician B
   3. Both A and B
   4. Neither A nor B

9. Technician A says that a 12-volt battery has six cells. Tech­nician B says that the more plates a cell in a battery has, the more voltage it creates. Who is correct?
   1. Technician A
   2. Technician B
   3. Both A and B
   4. Neither A nor B

10. Technician A says that the specific gravity of the electrolyte can be checked with a hydrometer. Technician B says that the specific gravity of the electrolyte can be checked with a refractometer. Who is correct?
    1. Technician A
    2. Technician B
    3. Both A and B
    4. Neither A nor B

Assignments

• Review all materials from this chapter and be prepared for a chapter quiz to be administered (date to be determined by instructor).
• Direct students to read the next chapter in Fundamentals of Automotive Maintenance and Light Repair, Second Edition as listed on your syllabus to prepare for the next class session.

Chapter 42

Meter Usage and Circuit Diagnosis

Learning Objectives

After reading this chapter, you will be able to:

• 42-01 Describe basic meter info.
• 42-02 Describe basic meter layout and ranges.
• 42-03 Describe special meter settings and probing techniques.
• 42-04 Describe how to measure volts, amps, and ohms.
• 42-05 Perform available voltage and voltage drop measurements.
• 42-06 Perform resistance measurements.
• 42-07 Perform current measurements.
• 42-08 Perform series circuit measurements.
• 42-09 Perform parallel circuit measurements.
• 42-10 Perform series-parallel circuit measurements.
• 42-11 Perform measurements on variable resistors.
• 42-12 Describe electrical circuit testing.
• 42-13 Perform voltage and voltage drop measurements.
• 42-14 Locate opens, shorts, grounds, and high resistance.
• 42-15 Test circuits with a test light and fused jumper wire.
• 42-16 Test circuit protection devices, switches, and relays.

ASE Education Foundation Tasks

The following ASE Education Foundation Automobile Accreditation Tasks are covered in this chapter:

• VIA4 Demonstrate proper use of a digital multimeter (DMM) when measuring source voltage, voltage drop (including grounds), current flow, and resistance.
• VIA5 Demonstrate knowledge of the causes and effects from shorts, grounds, opens, and resistance problems in electrical/electronic circuits.
• VIA6 Use a test light to check operation of electrical circuits.
• VIA7 Use fused jumper wires to check operation of electrical circuits.
• VIA9 Inspect and test fusible links, circuit breakers, and fuses; determine necessary action.

Readings and Preparation

• Review all instructional materials, including the chapter in Fundamentals of Automotive Maintenance and Light Repair, Second Edition, and all related presentation support materials.

Support Materials

• Lecture PowerPoint presentation, including all Skill Drills

Pre-Lecture

• You Are the Automotive Technician
  • A progressive case study that encourages critical thinking skills.
  • Direct students to read the “You Are the Automotive Technician” scenario found at the beginning of each chapter.
  • Group Activity: Direct students to review the discussion questions at the end of the scenario and prepare a response to each question. Facilitate a class discussion centered on the questions.
  • Homework Assignment: Ask students to turn in their comments on the questions.
• Teaching Tip: Explain to students how this material applies to the workplace. Provide an example of a situation to make it relevant and meaningful. How does it fit into the broader picture? Is it building on something they already know? Will it help them master a skill? Students need to understand that what we are teaching is of importance on the job. This can be done by describing situations where you have misused a meter or misdiagnosed an electrical fault based on faulty meter usage. You can also have students complete the online pre-test for this chapter in the CDX online system. This will help them understand what they do and do not know about meter usage systems.

Lecture

42-01 Describe basic meter info.

• Digital multimeters (DMMs) are tools for taking electrical measurements and are used to diagnose electrical faults.
• Basic DMMs can measure AC and DC voltages, AC and DC amperage, and resistance, whereas modern DMMs may be able to measure frequency and temperature with dedicated diode test capabilities.
• Most DMMs include one or more fast-blow fuses that blow if the amperage is too high, protecting the meter.
• CAT ratings indicate the power of the electrical systems that the meters are designed to work with.
• Hybrid and electric vehicles usually require meters and test leads rated as CAT III to CAT IV.

42-02 Describe basic meter layout and ranges.

• The DMM consists of the main instrument body and the test leads to connect it to the circuit.
• The instrument body has a function switch to choose the type of electrical measurement, a digital display to report the readings, and slots to connect the test leads.
• Test leads are available in pairs: one red and one black. They have a probe at one end to connect to the circuit being tested and a terminal at the other end that plugs into the slots on the DMM.
• Accessories such as temperature probes and inductive current clamps can convert temperature and current into a voltage that can be read by the DMM.
• DMMs read very small to very large quantities, making the use of a single range or scale impractical.
• DMM screens can only display four or five digits; symbols are used as substitute for some of the digits.
• Different ranges provide different resolutions. To achieve the most accurate readings, the lowest range possible should be selected.
• Most DMMs have an automatic ranging capability, but they do not provide warnings when changing ranges.

42-03 Describe special meter settings and probing techniques.

• When in the min/max setting, the DMM records the minimum and maximum readings obtained during the test.
• The hold function freezes the value currently on the display, and the auto-hold function holds the value on the display when a measurement is taken.
• “Common” refers to the slot being common to all functions of the meter, and the lead does not need to be moved when different functions are accessed.
• The red lead is called the probing lead, and it acts as a probe into the circuit. The meter screen always reads what the probing lead is touching compared to the common lead.
• Probes have voltage limits. When high-voltage measurements are being taken, probes designed for high voltage should be used.
• Standard probe leads supplied with the DMM are basic straight metal probes that are useful in making quick measurements.
• Back-probing is used to probe the back of a connector, using very fine pins that slip into the connector without causing damage.
• Insulation-piercing probes have sharp, fine pins that pierce the insulation and contact the wire. These probes can damage the insulation or the conductor and should be used rarely.

42-04 Describe how to measure volts, amps, and ohms.

• To measure volts, the red probing lead is connected to the volts/ohms slot, and the black common lead is connected to the common slot.
• The appropriate range and type of current being measured needs to be selected.
• The probing lead is connected to the positive side of the circuit being tested, and the common lead is connected to the negative post of the battery or to ground.
• To measure amperage, the red lead is connected to the A or mA slot, and the black lead is connected to the common slot.
• To measure current, the DMM must be connected in series with the circuit. One wire is disconnected and the meter leads are connected to each disconnected end of the circuit.
• The probing lead is connected closest to the positive terminal of the power supply or the battery.
• Current clamps are available in several current-measuring ranges; they are fastened around the conductor and measure the strength of the magnetic field produced by the current flowing through it.
• Current clamps output a voltage, hence the DMM is set to read volts when they are used.
• When measuring resistance, the red lead is connected to the volts/ohms slot and the black lead is connected to the common slot.
• The red lead is connected to the input side of the component, and the black lead is connected to the output side.
• The component must be disconnected or isolated from the circuit and the power disconnected when taking resistance measurements.

42-05 Perform available voltage and voltage drop measurements.

• Using the lowest range that will still provide a signal gives the most accurate reading.
• The voltage drops every time the current goes through a resistor.
• No current flows when the switch is open and zero voltage is used by the resistors.
• When the switch is closed, current flows through the entire circuit; each load uses some of the voltage, and the higher the resistance, the more voltage is used. All the voltage is used by the end of the circuit.
• The resistor with the most resistance always uses the most voltage in a series circuit, but the sum of voltage drops still equals the source voltage.
• Adding an additional resistor splits the voltage further, although the sum of all voltage drops will always equal the source voltage.
• Most loads are designed to operate on full battery voltage, so any voltage drop, before and after the load, reduces the available voltage and amperage to the load.
• This starves the load and reduces the power used by it, making it operate less effectively.
• As a voltmeter reads the difference in voltage between the two leads, placing one lead on the input of a component and the other on the output directly measures the voltage drop across it.

42-06 Perform resistance measurements.

• Ohm’s law states that current flow is inversely proportional to resistance: the higher the resistance, the less current will flow, and vice versa.
• Resistance in series adds up so the total circuit resistance is the sum of all the individual resistances.

• Resistance measurements are taken to check components or circuits against manufacturer specifications.
• To perform resistance measurements, the power should be disconnected, the red lead connected to the volts/ohms slot, and the black lead connected to the common slot.

• Ideally, the component should be disconnected from the circuit when taking resistance measurements.

42-07 Perform current measurements.

• Current flows produce a magnetic field around the conductor.
• The current through all parts of a series circuit is the same, so the ammeter should be connected in series within the circuit to ensure that all the current flowing through the circuit flows through the ammeter.
• To do this, the circuit should be broken in two and each end of the ammeter connected to one of the broken ends.
• Adding an additional resistance in a series circuit reduces the overall current in the circuit, though the current flow remains equal in all parts of the circuit.
• To measure current, the red lead should be connected to the A slot and the black lead to common.
• When energized, a relay winding produces a magnetic field, hence a compass needle can be used to indicate whether the relay is operating without removing it.

42-08 Perform series circuit measurements.

• Virtually all the voltage should be used up in the load on a properly operating circuit.
• If total resistance is doubled, the total current flow is reduced by half.
• Voltage drop is the same across two equal-resistance loads in series, and it is split unevenly between loads with unequal resistance values.
• The position of a load in a circuit does not change the voltage drop across it; that is, placing a larger load before or after a smaller load does not cause it to use voltage in the circuit.
• Adding additional loads increases the total resistance of a series circuit and reduces the total current flow.

42-09 Perform parallel circuit measurements.

• Resistance in a parallel circuit reduces as more parallel paths are added.
• Current flow from individual legs adds up in parallel while voltage stays the same at all common parallel circuit inputs.
• Adding another load in parallel reduces the total circuit resistance and increases the total amperage, while each load uses full source voltage.
• The current in each leg of a circuit with two unequal loads in parallel is proportional to its resistance.
• The total resistance in the circuit is still lower than the lowest resistance, and total current is the sum of the current flow in each leg.
• The voltage drop across one parallel branch is the same for all parallel branches, regardless of their resistance.

42-10 Perform series-parallel circuit measurements.

• To calculate the total resistance of a series-parallel circuit, the entire circuit should be converted to an equivalent series circuit.
• The total resistance of the parallel circuit should be calculated and added to the series resistance because the parallel portion is in series with the series circuit.
• The total current flow can then be calculated by dividing the total circuit voltage by the circuit resistance.
• The total current flows through the series load, and the total source voltage is shared between the series and parallel portions of the circuit.
• Each parallel load receives the full parallel circuit voltage while the amperage is split between each branch of the circuit according to its resistance.
• Adding an additional load in the parallel portion of the circuit reduces the total resistance of the parallel portion and hence the total resistance of the circuit.
• This increases the current flow in the circuit, creating voltage drop across the series load.
• Each parallel load also uses less power as it receives lesser voltage and the current through each branch is lesser.

42-11 Perform measurements on variable resistors.

• A variable resistor can provide an infinitely variable voltage reading from ground to input voltage.
• The current and voltage change as the variable resistor is adjusted; in practice, there may be a small amount of resistor left on the outer edges, so the voltage may not reach the full 12 or 0 volts.

42-12 Describe electrical circuit testing.

• Ohm’s law can be used to calculate electrical quantities in a circuit, and it can be compared to actual measured quantities to determine whether the circuit is functioning correctly.
• It is useful to understand the relationships between volts, amps, and ohms; they help identify what test is needed next during diagnosis.
• Amperage is a product of voltage and resistance; it is useful to observe whether the current is low or high.
• If the current is high, either the voltage is high or the resistance is low; if the current is low, either the voltage is low or the resistance is high.
• Measuring the battery voltage is a simple method to check for too much voltage. High and low resistances of components can be checked using an ohmmeter.

42-13 Perform voltage and voltage drop measurements.

• To test for unwanted voltage drop, the voltage across each part of the circuit should be measured—including conductors, switches, and connectors—and compared with specifications.
• The total voltage drop across each side of the whole circuit should not exceed 0.5 volts on a 12-volt circuit or 1.0 volts on a 24-volt circuit, and individual voltage drops across each wire connection or switch should not exceed 0.2 volts.
• The voltage drop across each side of the circuit should be measured first to identify which side of the circuit has the excessive voltage drop.
• For the positive side, the black voltmeter lead should be placed on the positive battery terminal and the red lead on the input of the load.
• For the negative side, the black lead should be placed on the negative battery terminal and the red lead on the output of the load. If either voltage reading is larger than 0.5 volt, the individual connections on that side of the circuit should be checked.
• If each side of the circuit is working properly, the load may be suspected to have a fault.
• Voltage drops may happen on the ground side, reducing the voltage and current available to the load.

42-14 Locate opens, shorts, grounds, and high resistance.

• Open circuits cause a voltage drop equal to the source voltage; the voltage drop test is first performed on each side of the circuit to determine which side is open and then continued on the open side to isolate the fault.
• If the voltage drop test on each side of the circuit is within specifications, an ohmmeter should be used to check if the load is open.
• High resistance may be caused by corroded or loose harness connectors, incorrectly sized cable for the circuit current flow, incorrectly fitted terminals, and poorly soldered joints.
• A voltage drop test may be conducted on the power and ground circuits; high resistance will cause the voltage drop to be less than battery voltage.
• If the high resistance is within the load, the resistance may be checked using an ohmmeter and compared to specifications.
• Shorts or short circuits usually cause lower than normal circuit resistance, which leads to abnormally high current, causing fuses or circuit breakers to open the circuit.
• A short to power may cause the circuit to remain live even after the switch is turned off.
• A short within a component is best tested by comparing its ohm reading to specifications.
• A short within a wire harness can be checked by disconnecting each end and using an ohmmeter to test for unwanted continuity between various wires.
• A short to ground will likely blow a fuse, if on the feed side, or cause the load to run every time the circuit has power, if on the ground side.
• To locate the short, the fuse and any loads on the fuse circuit should be disconnected, and the continuity checked between the fuse output and ground.
• If there is continuity, disconnect the connector between the fuse and load, check which side of the harness has continuity, and keep tracing to locate the fault.
• If there is no continuity, the resistance of each load should be checked for internal shorts.
• Another method to locate a short is to connect a test lamp or buzzer in place of the fuse. The current will flow through and find ground at the short; various parts of the circuit can be disconnected to narrow down the location of the short.
• Specialized detection tools send a signal through the wiring harness, and a receiving device indicates where the short is located when moved across the wire loom.
• Short to power is caused when power from one circuit leaks into another and can be diagnosed first with a voltmeter to check for unwanted voltage and then using an ohmmeter to isolate the problem in the wire harness.

42-15 Test circuits with a test light and fused jumper wire.

• Test lamps are useful to determine whether electrical power is present in a part of a circuit, but they should always be tested on known good power and ground before use.
• The test light needs both power and ground to be illuminated, so if the circuit is missing one of these elements, the light will not be illuminated.
• The voltage of the circuit being tested should not exceed the test light’s rating to avoid damaging the test light.
• Test lights should not be used on supplemental restraint systems (SRS) as this could cause the airbags to deploy.
• Using the test light on computer circuits designed for very small amounts of current could also damage the electronics inside the modules.
• Jumper leads can be used to extend test leads so that circuit readings can be taken with a DMM.
• They can also be used to jump across terminals on fuses, relays, or other components to bypass part of the circuit and provide an alternate power or ground source to the components being tested.
• The circuit should always be protected by a fuse of the correct size. The fuse also protects the jumper lead, though if power is supplied to the wrong part, it can still be over-powered and damaged.
• Fuses, fusible links, and circuit breakers are available in various ratings, types, and sizes and should always be replaced with the same rating and type.
• A good fuse has virtually the same voltage on both sides, whereas a blown fuse has battery voltage on one side and 0 volts on the other.
• If both sides of the fuse show 0 volts, the ignition may have to be turned on, or a fusible link or maxi-fuse supplying the fuse box may be burned open.
• Fuses should be visually inspected to ensure that the fusible element is intact and that the fuse and fuse holder are clean, are free of corrosion, and fit snugly together.
• If measured with an ohmmeter, the fuse should have very low resistance.

42-16 Test circuit protection devices, switches, and relays.

• Testing of electrical devices and wiring begins with visual inspection to find any breakage, corrosion, or deformity and includes examination of the insulation for any worn or melted spots.
• Switches, solenoid contacts, and relay contacts require electrical testing.
• Voltage drop tests on switches are performed by measuring the voltage from the input of the switch to the output while operating the circuit.
• Voltage drops of over 0.2 volts usually indicate high resistance on switches, while some starter solenoids might allow slightly larger voltage drops across the solenoid contacts.
• Relay contacts are tested like normal switches, whereas the winding is tested with an ohmmeter.
• Special tools are needed to test spike-protected relays with internal diodes, or a fresh 9-volt battery can be connected across the terminals; the relay should click in one direction and not the other.
• Some solenoids may be disassembled and visually inspected. The contacts will appear pitted and burned if there is excessive voltage drop across the contacts.

Post-Lecture

This section contains various student-centered end-of-chapter activities designed as enhancements to the instructor’s presentation. As time permits, these activities may be presented in class. They are also designed to be used as homework activities.

1. Direct students to read and individually answer the question sets located in the Wrap-Up section at the end of each chapter. Allow approximately 10–20 minutes for this part of the activity.
2. Facilitate a class review and discussion of the answers, allowing students to correct responses as may be needed. Use the answers noted in the Answer Key to assist in building this review.
3. You may wish to ask students to complete this activity on their own and turn in their answers on a separate piece of paper.

Review Questions

This question set is designed to assist students in understanding the chapter content by asking knowledge-based comprehension questions.

1. What is the minimum DMM rating for hybrid vehicles?
   1. CAT I
   2. CAT II
   3. CAT III
   4. CAT IV

2. A technician is setting up their DMM to take a voltage reading. Where should the black lead be installed in the meter?
   1. In the A slot
   2. In the V/Ω slot
   3. In the mA slot
   4. In the COM slot

3. All of the following are true about voltage in a functional series circuit, EXCEPT:
   1. All of the voltage gets used up by the end of the circuit.
   2. Each of the loads use up the same amount of voltage.
   3. Each load uses some of the voltage.
   4. The load with higher resistance uses more voltage.

4. When checking resistance what should the readings be compared to?
   1. Manufacturer’s specifications
   2. The owner’s manual readings
   3. The meter’s guide book
   4. Watt’s law

5. Which of the following is true about a series circuit?
   1. The current varies at different parts of the circuit.
   2. The resistance of every load is the same.
   3. An open in one load still allows the others to work.
   4. Nearly all the voltage should be used up in the load.

6. Which of the following is true about a parallel circuit?
   1. Circuit resistance goes up as more loads are added.
   2. Current flow in all legs are the same.
   3. Each load has access to the same voltage input.
   4. If one load is open, none of the other loads will work.

7. Which of the following is true about a series-parallel circuit?
   1. The total source voltage is shared between the series and parallel loads.
   2. The series loads and parallel loads have access to the same source voltage input.
   3. Adding a load in the series portion will reduce the total circuit resistance.
   4. Adding a load in the parallel portion will increase the total circuit resistance.

8. When performing an available voltage test on a circuit, which of the following should be performed first?
   1. Place the red lead before the load, and the black lead after the load.
   2. Place the red lead before the load and the black lead on a good ground.
   3. Measure the source voltage of the battery using your red and black leads.
   4. Check the condition of the ground using voltage drop to check the negative battery terminal.

9. When testing a circuit with a test light, what must be done first?
   1. Power on the test light by pressing its ON button.
   2. Turn off power to the circuit before testing.
   3. Set the test light to the correct voltage range.
   4. Test the light with a known good power and ground.

10. What type of circuit protection device can be reset?
    1. A fuse
    2. A fusible link
    3. A relay
    4. A circuit breaker

ASE Technician A/Technician B Style Questions

This question set is designed to assist students in gaining a further understanding of and familiarity with ASE Technician A/Technician B questions.

1. A voltage reading is being taken using a DMM. The screen reads 4997 mv. Technician A states that this is 0.4997 volts. Technician B states that this reading is equivalent to 4.997 volts. Who is correct?
   1. Technician A
   2. Technician B
   3. Both A and B
   4. Neither A nor B

2. A throttle position sensor is being checked with a DMM. Technician A states that the DMM sample rate may be too slow, and an oscilloscope would likely have a faster sample rate. Technician B states that the min/max function can be used to assist the technician in finding an electrical fault in the sensor. Who is correct?
   1. Technician A
   2. Technician B
   3. Both A and B
   4. Neither A nor B

3. Two technicians are discussing measuring resistance. Technician A states that power should be applied to the circuit when checking resistance. Technician B states that when checking resistance on manual range, start at the highest range and work your way down. Who is correct?
   1. Technician A
   2. Technician B
   3. Both A and B
   4. Neither A nor B

4. Two technicians are discussing measuring current in a circuit. Technician A states that the circuit must be opened and the DMM inserted in series. Technician B states that the circuit must be powered off to measure current. Who is correct?
   1. Technician A
   2. Technician B
   3. Both A and B
   4. Neither A nor B

5. Variable resistors are being discussed. Technician A states that variable resistors can be used to indicate position. Technician B states that a potentiometer is a type of variable resistor. Who is correct?
   1. Technician A
   2. Technician B
   3. Both A and B
   4. Neither A nor B

6. An electrical circuit is being discussed. Technician A states that if voltage stays the same, but resistance increases, current must increase. Technician B states that if voltage decreases, and resistance stays the same, current will increase. Who is correct?
   1. Technician A
   2. Technician B
   3. Both A and B
   4. Neither A nor B

7. A voltage drop test is being discussed. Technician A states that the black lead should be placed on the negative terminal of the battery, and the red lead at the input of the load. Technician B states that the red lead should be placed at the input of the load, and the black lead at the positive battery terminal. Who is correct?
   1. Technician A
   2. Technician B
   3. Both A and B
   4. Neither A nor B

8. A short to ground is being discussed. Technician A states that if the short to ground is before the load, it will cause excessive current. Technician B states that a short to ground after the load will cause a fuse to blow. Who is correct?
   1. Technician A
   2. Technician B
   3. Both A and B
   4. Neither A nor B

9. Two technicians are discussing testing a circuit with a test light. Technician A states that if a test light illuminates, it is receiving power and ground. Technician B states that test lights should never be used with supplemental restraint systems. Who is correct?
   1. Technician A
   2. Technician B
   3. Both A and B
   4. Neither A nor B

10. A relay is being tested. Technician A states that the relay winding can be tested with an ohmmeter while it is powered on. Technician B states that some relays use a diode for circuit protection, and they require different tests than conventional relays. Who is correct?
    1. Technician A
    2. Technician B
    3. Both A and B
    4. Neither A nor B

Assignments

• Review all materials from this chapter and be prepared for a chapter quiz to be administered (date to be determined by instructor).
• Direct students to read the next chapter in Fundamentals of Automotive Maintenance and Light Repair, Second Edition as listed on your syllabus to prepare for the next class session.

Chapter 41

Electrical Components and Repair

Learning Objectives

After reading this chapter, you will be able to:

• 41-01 Describe electrical switches.
• 41-02 Describe circuit protection devices.
• 41-03 Describe the operation of relays and solenoids.
• 41-04 Describe the basic operation of motors and transformers.
• 41-05 Describe the common types of resistors.
• 41-06 Describe wire.
• 41-07 Describe wire harnesses.
• 41-08 Use wiring diagrams to trace circuits.
• 41-09 Replace wire terminals.
• 41-10 Perform solder repairs.

ASE Education Foundation Tasks

The following ASE Education Foundation Automobile Accreditation Tasks are covered in this chapter:

• VIA3 Use wiring diagrams to trace electrical/electronic circuits.
• VIA10 Repair and/or replace connectors, terminal ends, and wiring of electrical/electronic systems (including solder repair).
• VIA11 Identify electrical/electronic system components and configuration.

Readings and Preparation

• Review all instructional materials, including the chapter in Fundamentals of Automotive Maintenance and Light Repair, Second Edition, and all related presentation support materials.

Support Materials

• Lecture PowerPoint presentation, including all Skill Drills

Pre-Lecture

• You Are the Automotive Technician
  • A progressive case study that encourages critical thinking skills.
  • Direct students to read the “You Are the Automotive Technician” scenario found at the beginning of each chapter.
  • Group Activity: Direct students to review the discussion questions at the end of the scenario and prepare a response to each question. Facilitate a class discussion centered on the questions.
  • Homework Assignment: Ask students to turn in their comments on the questions.
• Teaching Tip: Explain to students how this material applies to the workplace. Provide an example of a situation to make it relevant and meaningful. How does it fit into the broader picture? Is it building on something they already know? Will it help them master a skill? Students need to understand that what we are teaching is of importance on the job. This can be done by describing interesting electrical system repairs you have experienced. You can also have students complete the online pre-test for this chapter in the CDX online system. This will help them understand what they do and do not know about electrical system repairs.

Lecture

41-01 Describe electrical switches.

• Electrical components are used to modify or manage the flow of electric current in a circuit; switches, fuses, circuit breakers, resistors, capacitors, and relays are some examples.
• Some components are polarity sensitive and should only be connected into the circuit with the correct polarity; some capacitors and most semiconductor components are polarity sensitive.
• A switch is used to turn current on and off in a circuit; when turned off, the switch opens the circuit and stops the flow of current; and when turned on, the switch closes the circuit and allows the current to flow.
• Switches are of many types and may be toggle switches, push-button switches, specialty switches, and momentary switches.
• Switches may be basic two-terminal toggle switches or more complex with many terminals and contacts inside them.
• Circuit or schematic diagrams, also called wiring diagrams, show switches and their surrounding circuits with the terminals on the switch numbered or lettered, as well as the terminal identification of the mating connectors.

41-02 Describe circuit protection devices.

• Fuses and circuit breakers protect electrical circuits by opening the circuit if the current flow is excessive.
• The most common kinds of circuit protection devices are fuses, fusible links, circuit breakers, and positive temperature coefficient (PTC) thermistor protection devices.
• Fuses and circuit breakers are rated in amps, whereas fusible links are rated by wire size.
• A fuse contains a precisely shaped metal strip that melts when subjected to current above a specified level. This breaks the circuit permanently and prevents potential damage to the wiring harness and more valuable components.
• Fuses are available in a number of configurations and amp ratings, with blade fuses being the most commonly used in automotive applications.
• Fuses are typically housed in fuse boxes located around the vehicle. These may be under the hood, under the dash, or sometimes in the trunk, and may also include relays and diodes.
• A fusible link is made of a smaller diameter wire of short length, which has a lower melting point and fire-resistant insulation.
• It is commonly used to protect the wiring harness between the battery and any fuse boxes.
• They typically carry more current than fuses and feed power to more than one circuit.
• Fusible links do not fail often, and if they do, it is usually due to a substantial short in the circuit.
• Fusible links may also fail due to excessive flexing or pulling. Some newer vehicles use large blade-type fuses called maxi-fuses instead.
• Circuit breakers differ from fuses and fusible links. They are not destroyed by excessive current and can usually be reset, either manually or automatically.
• In a circuit breaker, a bimetallic strip heats up and opens a set of contacts when the current becomes excessive. Usually, as the strip cools it returns to its original shape and closes the circuit again.
• A PTC thermistor generates heat due to the voltage drop; if too much current flows through it, this increases the resistance of the thermistor and further increases the voltage drop.
• This cycle continues quickly until the PTC reaches its maximum resistance, which effectively shuts off most of the current flow to the protected device.
• They generally reset once the power is removed and they are allowed to cool; they are usually incorporated into power window motors and door locks.
• A flasher can is the control mechanism for the turn signals.
• Flasher cans are generally mechanical devices, and flasher controls are generally electronic.
• Flasher cans operate like automatically resetting circuit breakers and use a bimetallic strip to open and close the switch contacts.
• They produce a distinctive clicking sound, which is used along with turn signal indicator lights to tell the driver when the turn signals are active.
• Electronic flasher controls control the on/off function electronically and can operate over a wider range of current flow, making them ideal for trailer towing.

41-03 Describe the operation of relays and solenoids.

• Relays are switches that are activated by a small electrical current and are used to control a larger current with a smaller current.
• Most electrical components are controlled using relays; electronic control units (ECUs) use relays to control components that carry large electrical loads such as the fuel pump, headlights, and cooling fan.
• A relay consists of a set of switch contacts, an electromagnet, terminals, and the case.
• When the relay coil is activated, the electromagnet pulls a moveable armature blade contact and sends power to the controlled device.
• A solid-state relay uses transistorized circuitry to turn the circuit on and off and does not make any sound unless designed to do so.
• Automotive relay terminals use one of two standard labeling systems: 85 or 1 indicates one end of the relay winding, 86 or 2 indicates the other end of the relay winding, 30 or 3 indicates the common-movable switch contact, 87a or 4 indicates the normally closed fixed contact to the common, and 87 or 5 indicates the normally open fixed contact to the common.
• When electromagnetic relays are de-energized, the collapsing magnetic field can cause a voltage spike, which can be transmitted into the circuit and damage electronic components.
• Some relays use a suppression diode or resistor in parallel with the winding coil to shunt the voltage to the input side of the coil so as to dissipate it in the loop.
• A solenoid consists of an insulated wire wound around a hollow tube; a mild steel core is fitted into the tube and is attracted by the magnetic field generated when the winding is energized.
• Solenoids can be used to push or pull and can produce large mechanical force.
• They may incorporate return springs, multiple windings, electrical contacts, and mechanical connections.

41-04 Describe the basic operation of motors and transformers.

• Electric motors consist of a field made of either electromagnets or permanent magnets and an armature containing electromagnetic coils that can be turned on and off.
• The interaction of the two magnetic fields produced causes the armature to rotate.
• The armature consists of a number of individual windings with two ends, each connected to a copper bar.
• The bars make up the segmented commutator, which receives electric current through two carbon brushes, allowing the electrical connection to be maintained as the armature is spinning.
• This continuously changes the orientation of the magnetic field, which keeps the armature spinning.
• Ignition coils and transformers work on the principle of electromagnetic induction; an ignition coil is like a step-up transformer that raises the output voltage much higher than the input voltage, whereas a step-down transformer reduces the output relative to the input.
• They consist of a primary winding made of 200 to 300 turns of light-gauge wire wound around 30,000 to 60,000 turns of very fine wire.
• A current passed through the primary winding creates a magnetic field that surrounds both windings.
• When the current is removed, the collapse of the magnetic fields induces a high voltage in the primary winding, and because the voltage generated is dependent on the number of coils, an extremely high voltage results in the secondary winding.
• This voltage is high enough to push current across the spark plug gap and create a spark.

41-05 Describe the common types of resistors.

• Resistors reduce the current in a circuit and induce a voltage drop; they are used to control the voltage and amperage going to various components.
• Fixed resistors are usually cylindrical in shape with axial leads projecting out from either end. They have a series of colored stripes painted on them that indicate their resistance and tolerance levels.
• Resistors are rated in ohms and have a power rating determined by their size.
• The colored bands on a resistor each represent a numeric value and are read from left to right, with the last band spaced farther apart, indicating the tolerance.
• Variable resistors can change their value by the movement of a slide or with temperature change.
• They may be linear, with their resistance value varying proportionally across their range, or nonlinear, meaning that their resistance change is not linear.
• A rheostat is a mechanical variable resistor with a resistor coil connected to one end of the supply and a wiper that can be moved over the coil manually to send current to the controlled device.
• If the wiper is close to the beginning of the coil, the resistance value is very small, and if the wiper is close to the end of the coil, the resistance value is very large.
• A potentiometer alters the voltage in a circuit and consists of a resistance wire wrapped between two fixed connections, one of which is connected to the supply and the other to ground.
• A third connection can be moved across the coil, and the variable voltage output is taken from this connection.
• A thermistor changes resistance values with temperature and may be of two types: negative temperature coefficient (NTC) and positive temperature coefficient (PTC).
• Resistance increases with an increase in temperature in PTC thermistors and decreases with increased temperature in case of NTC thermistors.

41-06 Describe wire.

• Wires carry electrical power and signals through the vehicle and are bundled together in wiring harnesses to protect them and keep them organized.
• Automotive wire typically has a multi-stranded copper core and seamless plastic insulation.
• Ribbon cable is a series of wires formed side by side and joined along the insulation so they lie flat.
• The ribbon design allows the wires to be routed neatly in groups and is commonly used as connections within printed circuits and between printed circuits and other components.
• Signal wires and communication wires are shielded to prevent electromagnetic interference, also called noise.
• It is important to use the correct wire for the application, as wires that are too small may cause excessive voltage drop and may get hot enough to melt the insulation, whereas wires that are too large will increase the cost, weight, and size of the wiring harness.
• The resistance of a wire is determined by its length, diameter, material, and temperature.
• Wire size is measured in two scales: the metric wire gauge measures the area of the conductor in square mm, and the American wire gauge (AWG) uses a rating number that increases as the current-carrying capacity decreases.
• Wire size charts specify how much current each wire gauge can safely carry. Many charts allow up to a 10 percent voltage drop over the length of the wire, which is significantly more than allowed in most automotive circuits.
• A wire may be described as 5,0 indicating a cross-sectional metric area of 5 mm squared or as 10/0.5 indicating 10 strands of wire each with a cross-sectional area of 0.5 mm squared, this system can also be applied to the AWG rating system using the gauge size.

41-07 Describe wire harnesses.

• Wiring harnesses, also known as wiring looms or cable harnesses, are used throughout the vehicle and are typically placed within a sheath of tubing or insulating tape.
• There are usually several wiring harnesses inside a vehicle, and they are attached using harness fasteners such as body clips or wire ties.
• Terminals are installed on the ends of wires to provide low-resistance termination, and they allow wires to be connected and disconnected.
• There are many different types and sizes of terminals to suit various wire sizes and termination requirements. Some of these are push-on spade terminals, eye ring terminals, butt connectors, and male/female terminals.
• Most terminals are crimp type, which require the use of special crimp tools to crimp the terminals to the end of the wire.
• Solder-type terminals require the use of soldering irons, flux, and solder to make the connection. Only rosin or rosin-core solder should be used when soldering wiring because acid-core solder can cause corrosion and high resistance over time.
• Terminals can be grouped together inside a connector housing (also called a wiring harness connector) and have male and female sides that are shaped so they can be fit together in only one way.
• Many of these connectors have locking mechanisms and are weatherproof to keep moisture out.
• To prevent electromagnetic induction noise, vehicles may use shielded wiring harnesses, which may be one of three forms: twisted pair, Mylar tape, or drain lines.
• Twisted pair uses two uniformly twisted wires to deliver signals between common components with a terminating resistor at the end. This cancels out any noise that occurs on the wires and reduces the loss of data in the transmitted signals.
• Mylar tape is electrically conductive material that is wrapped around the wiring harness inside or outside the outer harness layer.
• Any noise is absorbed by the Mylar and conducted to ground through a ground connection.
• A drain line is a non-insulated wire that is wrapped within a wiring harness and connected to ground at the source end of the harness. It conducts any noise to ground.

41-08 Use wiring diagrams to trace circuits.

• Wiring diagrams map all electrical components and their connections and use symbols to represent the various electrical components.
• As modern vehicles use many interconnected components, a single wiring diagram would be very difficult to use; therefore, wiring diagrams are split into systems and sub-systems to make them easier to use.
• To assist in understanding wiring diagrams, manufacturers supply keys for the diagrams containing component symbols and their names, color codes of the wires, harness connector identification, and pin numbers.
• In many cases, the diagrams are set up with power at the top and ground at the bottom, making it easier to follow the flow of electricity.
• Wiring diagrams are critical to diagnosing electrical faults; they help in understanding how the circuit was designed, determining how electricity flows through the circuit, and predicting what voltages should be present at the various connection points.
• Knowing the expected voltages allows the technician to measure the actual voltages and compare them to the expected values, then use them to trace the source of the fault.

41-09 Replace wire terminals.

• Wires are usually trouble-free and long-lasting. Issues with wiring are more likely to be due to the terminals than with the wires themselves.
• Wires may also be damaged due to physical breakage from excessive flexing or stress, pinching between components, or melting from contact with hot components.
• When electrical wires are joined to other wires or connected to a terminal, the insulation needs to be removed.
• Wire strippers are available in various configurations and remove insulation without damaging the wire strands. Using a blade or knife often cuts away some of the strands of wire, effectively reducing the current carrying capacity of the wire.
• Insufficient bare wire may not achieve a good connection, and excessive bare wire may expose it to potential shorts with other circuits or to ground.
• If a wire itself needs to be repaired, it should be soldered back together.
• Solderless terminals are used primarily at connectors that are designed to be disconnected.
• They are quick to install but require a clean, tight connection, so it is important to ensure that the wire and connection are clean before attaching any terminals.
• Many solderless connectors are color coded for the size of the wire they fit.
• Many manufacturers use special crimping tools; using the wrong type of tool will cause connections to have poor grip on the wire and may damage the terminal.

41-10 Perform solder repairs.

• Solder is typically made from 60% tin and 40% lead and is available as solid or flux cored.
• Flux is needed to prevent the metals from being oxidized when heated and can have either an acid or rosin base.
• Acid flux is used on nonelectrical metal joints such as radiators, and must be removed after soldering to prevent the joint from corroding.
• Rosin flux is used on electrical connections because it is much less likely to corrode metals.
• Solder is applied using a hot soldering iron, which may be heated electrically or by an external source such as a butane torch.
• The soldering iron absorbs heat, which is then transferred to the wires that are to be joined. Once the wires are hot enough, the solder can be melted between the wires.
• Cleaning the soldering iron may involve heating the tip and cleaning it with a damp cloth or using a file to remove oxidized metal.
• Tinning the soldering iron involves heating the tip and applying a small amount of solder to it.
• Overheating the wire during soldering can cause the solder to be drawn too far up the wire, creating a long, nonflexible joint susceptible to breaking, or it may cause the insulation to melt.
• Heat shrink tubing may be used to protect the joint after soldering or, if unavailable, electrical insulation tape may be used.

Post-Lecture

This section contains various student-centered end-of-chapter activities designed as enhancements to the instructor’s presentation. As time permits, these activities may be presented in class. They are also designed to be used as homework activities.

1. Direct students to read and individually answer the question sets located in the Wrap-Up section at the end of each chapter. Allow approximately 10–20 minutes for this part of the activity.
2. Facilitate a class review and discussion of the answers, allowing students to correct responses as may be needed. Use the answers noted in the Answer Key to assist in building this review.
3. You may wish to ask students to complete this activity on their own and turn in their answers on a separate piece of paper.

Review Questions

This question set is designed to assist students in understanding the chapter content by asking knowledge-based comprehension questions.

1. A switch is used to:
   1. protect a circuit.
   2. allow current to flow only one way.
   3. reduce the current flow.
   4. turn current flow on and off.

2. Fuses prevent circuit damage by:
   1. stopping excessive current flow.
   2. reducing wiring length.
   3. limiting voltage increases.
   4. decreasing circuit resistance.

3. By using a small current in the relay winding, the contacts in the relay controls:
   1. a larger current.
   2. a smaller current.
   3. the exact same amount of current.
   4. the amperage at which the fuse blows.

4. The two main components of motors are the armature and:
   1. the field.
   2. the commutator.
   3. the brushes.
   4. the magnets.

5. Which of these is NOT a type of resistor?
   1. Stationary resistor
   2. Thermistor
   3. Variable resistor
   4. Fixed resistor

6. If a wire is described as being metric size of 8.0 it is:
   8. 0 mm² cross-sectional area.
   9. 0 cm² cross-sectional area.
   10. 8 inch² cross-sectional area.
   11. 8 mm² cross-sectional area.

7. Learning to read wiring diagrams takes a bit of time and experience, but knowing that circuits usually consist of __________ and a ground is a good start.
   1. a power source
   2. a switch
   3. a load
   4. All of the above

8. The type of solder that is safe for electrical wires and incorporates flux in the core of the solder is referred to as:
   1. rosin cored solder.
   2. acid cored solder.
   3. silver solder.
   4. tinning solder.

9. Shielded wiring harnesses primarily help prevent:
   1. wires from chaffing.
   2. unwanted short circuits between wires.
   3. wires from becoming corroded.
   4. unwanted electromagnetic induction.

10. When stripping wire insulation:
    1. use a knife or razor blade.
    2. strip off at least 0.5″ beyond the joint or terminal.
    3. strip off no more than 0.5″ at a time.
    4. use a propane torch to soften the insulation first.

ASE Technician A/Technician B Style Questions

This question set is designed to assist students in gaining a further understanding of and familiarity with ASE Technician A/Technician B questions.

1. Two technicians are discussing solder repair. Technician A says that solder should be applied to the soldering iron tip while soldering. Technician B says that the solder should be applied to the wire joint while soldering. Who is correct?
   1. Technician A
   2. Technician B
   3. Both A and B
   4. Neither A nor B

2. Two technicians are discussing wiring diagrams. Technician A says that wire colors are listed. Technician B says that connectors are listed. Who is correct?
   1. Technician A
   2. Technician B
   3. Both A and B
   4. Neither A nor B

3. Technician A says that 18-gauge AWG wire can carry more current flow that 12-gauge AWG wire. Technician B says that metric wire is sized by its cross-sectional area. Who is correct?
   1. Technician A
   2. Technician B
   3. Both A and B
   4. Neither A nor B

4. Two technicians are discussing circuit protection devices. Technician A says that fusible links are short sections of special conductor material, used to protect wires such as between the battery and fuse box. Technician B says that automotive circuit breakers are generally designed to automatically reset if they are tripped. Who is correct?
   1. Technician A
   2. Technician B
   3. Both A and B
   4. Neither A nor B

5. Technician A says that some relays are equipped with a suppression diode in parallel with the winding. Technician B says that some relays are equipped with a resistor in parallel with the winding. Who is correct?
   1. Technician A
   2. Technician B
   3. Both A and B
   4. Neither A nor B

6. Technician A says that a twisted pair is two wires, twisted together, that deliver signals between common components. Technician B says that in many cases, wiring diagrams are set up with power on the top of the diagram and ground on the bottom. Who is correct?
   1. Technician A
   2. Technician B
   3. Both A and B
   4. Neither A nor B

7. Technician A says that solderless terminals are universal in size meaning that any terminal can be used with any size wire. Technician B says that many manufacturers use special crimping tools. Who is correct?
   1. Technician A
   2. Technician B
   3. Both A and B
   4. Neither A nor B

8. Two technicians are discussing an electric motor. Technician A says that a set of carbon brushes transfer electricity to the bars on the commutator. Technician B says that the armature has one long winding. Who is correct?
   1. Technician A
   2. Technician B
   3. Both A and B
   4. Neither A nor B

9. Technician A says relays are turned on and off by a small amount of current. Technician B says many relays have both normally closed (NC) and normally open (NO) contacts. Who is correct?
   1. Technician A
   2. Technician B
   3. Both A and B
   4. Neither A nor B

10. Technician A says that most switches have numbered or lettered terminals. Technician B says that momentary switches can only be used once, then they need to be replaced. Who is correct?
    1. Technician A
    2. Technician B
    3. Both A and B
    4. Neither A nor B

Assignments

• Review all materials from this chapter and be prepared for a chapter quiz to be administered (date to be determined by instructor).
• Direct students to read the next chapter in Fundamentals of Automotive Maintenance and Light Repair, Second Edition as listed on your syllabus to prepare for the next class session.
•  

Chapter 40

Principles of Electrical Systems

Learning Objectives

After reading this chapter, you will be able to:

• 40-01 Describe the importance of learning electrical theory.
• 40-02 Explain conductor, insulator, and semiconductor materials.
• 40-03 Describe the process of electron movement in a simple circuit.
• 40-04 Explain volts, amps, ohms, power, and ground.
• 40-05 Describe the sources of electricity.
• 40-06 Describe the effects of electricity.
• 40-07 Use Ohm’s law to calculate values.
• 40-08 Use Watt’s law to calculate values.
• 40-09 Describe series circuits and use its laws to calculate values.
• 40-10 Describe parallel and series-parallel circuits and calculate values.
• 40-11 Describe DC and AC and Kirchhoff’s current law.
• 40-12 Explain how to use electrical concepts to solve problems.

ASE Education Foundation Tasks

The following ASE Education Foundation Automobile Accreditation Tasks are covered in this chapter:

• VIA2 Demonstrate knowledge of electrical/electronic series, parallel, and series-parallel circuits using principles of electricity (Ohm’s law).

Readings and Preparation

• Review all instructional materials, including the chapter in Fundamentals of Automotive Maintenance and Light Repair, Second Edition, and all related presentation support materials.

Support Materials

• Lecture PowerPoint presentation, including all Skill Drills

Pre-Lecture

• You Are the Automotive Technician
  • A progressive case study that encourages critical thinking skills.
  • Direct students to read the “You Are the Automotive Technician” scenario found at the beginning of each chapter.
  • Group Activity: Direct students to review the discussion questions at the end of the scenario and prepare a response to each question. Facilitate a class discussion centered on the questions.
  • Homework Assignment: Ask students to turn in their comments on the questions.
• Teaching Tip: Explain to students how this material applies to the workplace. Provide an example of a situation to make it relevant and meaningful. How does it fit into the broader picture? Is it building on something they already know? Will it help them master a skill? Students need to understand that what we are teaching is of importance on the job. This can be done by describing interesting electrical system faults you have experienced. You can also have students complete the online pre-test for this chapter in the CDX online system. This will help them understand what they do and do not know about electricity and electrical systems.

Lecture

40-01 Describe the importance of learning electrical theory.

• The popularity of hybrid and electric vehicles shows that a technician’s understanding and application of electrical principles is critical.
• Electricity is made of tangible objects.
• The movement of these particles from one place to another is called electricity.
• It must be directed at components that can extract energy from the moving particles such as lights and electric motors.

40-02 Explain conductor, insulator, and semiconductor materials.

• All matter is made of atoms, which are made of positively, negatively, and neutrally charged particles.
• The nucleus has at least one positively charged proton and typically one or more neutrons, with negatively-charged electrons moving around it.
• The electrons orbit the nucleus in successive, concentric spherical shells, with each shell having a specific electron capacity and any further electrons having to be accommodated in farther out shells.
• If the atom has equal number of electrons and protons, the charges cancel out, leaving the atom in a balanced state with no overall charge.
• An atom with more electrons than protons is negatively charged, whereas an atom with fewer electrons than protons is positively charged; such imbalanced atoms are called ions.
• If a negative and positive ion are close enough, electrons can move from atom to atom; this flow is called current flow.
• Some materials contain lots of atoms with free electrons, which are electrons located on the outer shells of the atom and are very loosely held to the nucleus.
• They move more freely between atoms at the application of electrical potential (voltage).
• Conductors typically have fewer than 4 electrons in the outermost or valence ring and a single electron by itself is the most loosely held by the nucleus.
• Any substance, including air, will conduct electricity if sufficient voltage or electrical pressure is applied, although the term conductor is usually used to describe materials that allow electrons to flow with little resistance.
• Most metals conduct electricity, with copper being the most commonly used in automobiles.
• Materials that do not conduct electricity easily are called insulators; such materials do not allow current to flow easily, because their electrons are bound more tightly to the nucleus, and as a result, they have more than four electrons in the valence shell.
• Atoms with four electrons in the valence shell are considered semiconductors.
• Semiconductors conduct electricity easier than insulators but not as well as conductors. They can switch from being a conductor to an insulator and are used to make electrical components such as transistors and microchips.

40-03 Describe the process of electron movement in a simple circuit.

• For electrons to flow they need a complete pathway, called a circuit, and an electromotive force supplied by the battery, usually called voltage and measured in volts.
• Free electrons are repelled from the negative terminal and attracted by the positive terminal of the battery; this flow is called current flow or amperage and is measured in amps.
• The greater the voltage, the stronger it pushes on the electrons, causing greater flow and higher amperage.
• The current flow in a circuit is also affected by electrical resistance, which slows down the movement of electrons in a circuit and is measured in ohms.
• All materials have some resistance, even good conductors. The amount of resistance is determined by the type of material, the length of the conductor, the diameter of the conductor, and the temperature of the conductor.
• A resistor is a component designed to extract energy from the current as it flows through it, and usually has a set resistance, which is marked or coded on its surface.
• Current flowing through resistance generates heat.
• Resistance is constant under most conditions, except temperature change, and does not depend on the voltage or current passing through it.
• Electrical circuits can be very basic, consisting of a power supply, a fuse, a switch, a component that performs work, and wires connecting them all together.

40-04 Explain volts, amps, ohms, power, and ground.

• Voltage is the potential difference or the electrical pressure between the positive and negative battery terminals, measured in volts; a typical car battery is 12 volts.
• Current flow or amperage is measured in amps; it is measured by placing an ammeter in the circuit so the current flows through it.
• The unit for electrical resistance is the ohm; the higher the resistance, the less current that will flow in the circuit for any particular voltage.
• An ohmmeter is used to measure the resistance of a component after it is disconnected from the circuit.
• Power, source, or feed refers to the supply side of the circuit or the positive battery terminal.
• Ground refers to the return side of the circuit or the negative battery terminal.
• Vehicles commonly connect the chassis, body, and engine block to the negative terminal, as this reduces the amount of wiring needed in the vehicle.

40-05 Describe the sources of electricity.

• Electricity can be produced by the movement of a conductor through a magnetic field, the application of pressure to a special type of crystal, the conversion of sunlight by solar cells, and chemical reactions.
• Static electricity can be produced by rubbing two insulators together. During this process, one material loses electrons to the other.
• If these two charged surfaces are brought close together, it may create a spark as electrons leap across the gap. This can ignite fuel vapors and cause explosions.
• If two different metals are joined and heated, a small current can be generated. The joined metals are called a thermocouple.
• Thermocouples are used to measure the temperature of hot components and exhaust gases.
• If two dissimilar metals are immersed in an acidic liquid called an electrolyte, they produce ions, which allow the flow of electricity through a process called electrolysis.
• This principle is applied in the standard lead-acid battery used in most vehicles.
• Solar or photovoltaic cells contain semiconducting materials that directly convert sunlight into electricity.
• These cells are used in sun load sensors for automatically dimming headlights.
• Electrical potential is generated in some crystals when mechanical stress is applied to them. The reverse is also true, with potential difference applied across the crystal, causing physical distortion.
• Knock sensors, pressure sensors, and some electronic fuel injectors use such crystals, also called piezoelectric crystals.
• Electromagnetic induction is the flow of current in a conductor subjected to a varying magnetic field.
• The direction of the movement determines the direction of the current produced. A wire rotating in a magnetic field or a magnet rotated next to a winding will produce alternating current as the direction of the field change every half revolution.
• Electromagnetic induction is used in alternators, ignition coils, and some sensors with the amount of induction being dependent on the strength of the magnetic field, the number of windings, the speed of movement, and the relative distance between the field and the winding.

40-06 Describe the effects of electricity.

• Light, heat, chemical reactions, and magnetism are all effects of the flow of electricity and may be the primary reason for it.
• Heat is created as current flows through any kind of resistance. This effect is used in components such as window defoggers and circuit breakers.
• Electricity can create chemical reactions, such as the battery charging system, which reverses the current flow through the battery, forcing the sulfuric acid out of the lead plates and strengthening the electrolyte, recharging the battery.
• A light-emitting diode is a semiconductor diode that produces light by emitting photons when a current flows across its PN junction.
• Electricity also creates magnetic effects when it passes through a conductor and can be used to create mechanical movement such as in a relay or electric motor.

40-07 Use Ohm’s law to calculate values.

• Ohm’s law mathematically describes the relationship between volts, amps, and ohms.
• It shows that if one of these three units changes, one of the other two must also change and it takes one volt to push one amp through one ohm resistance.
• Depending on the value to be determined, one of the three formulas may be applied: A = V/R, V = A×R, R = V/A, where R stands for resistance, V for voltage, and A for amperage.
• The values must always be balanced, and as long as two values are known the third can be calculated.
• Using Ohm’s law, the expected values in a circuit can be calculated and compared to measured values to determine if an electrical fault exists.

40-08 Use Watt’s law to calculate values.

• Power is the rate at which work is performed, and is also known as the rate of transforming energy.
• Electrical power is measured in watts and is the rate at which electrical energy is transformed into another kind of energy.
• The power equation states that one watt of power is produced when one volt is used to push one amp through a resistance, and is given by P = V×A.
• The power equation can be simplified and transposed, thus: voltage equals power divided by amps (V = P/A), and amps equals power divided by voltage (A = P/V).
• This can be applied to any circuit where the voltage and current are known. If one of these values is not known, Ohm’s law can be used to determine it.

40-09 Describe series circuits and use its laws to calculate values.

• A series circuit is the simplest type of electrical circuit in which there is only one path for current to flow.
• The amperage is equal everywhere within a series circuit, and if there is more than one resistance in the circuit, they are connected one after the other; hence the total resistance in a series circuit is the sum of all the individual resistances.
• At each point in the circuit when the current flows through a resistance, a voltage drop occurs. This is desirable when it occurs within an intended load and undesirable when it occurs outside of intended loads.
• Current flow is the same in all parts of a series circuit and does not add up or drop.
• Voltage drops as current goes through resistances in series, and the source voltage is equal to the sum of individual voltage drops in the circuit (Kirchhoff’s voltage law).
• Total resistance in a series circuit is the sum of the individual resistances.

40-10 Describe parallel and series-parallel circuits and calculate values.

• In a parallel circuit there is more than one path for current to flow.
• Any break in a series circuit causes current to stop flowing to all the components in the circuit; however, if any component or connection fails in one branch of a parallel circuit, current continues to flow normally to the remaining branches.
• The voltage is the same at the input of all branches of a parallel circuit and the voltage drop across all branches is also the same.
• The total current flowing through the circuit is the sum of the current flowing in each branch of the circuit.
• The total resistance of a parallel circuit decreases as more branches are added, and the total resistance of the circuit is always lower than the branch with the lowest resistance.
• Adding more branches to a parallel circuit provides more pathways for the current to flow, thus decreasing the overall resistance of the circuit.
• A series-parallel circuit is made of both a series and parallel circuit. The series portion may be before or after the parallel portion of the circuit.
• These circuits may be analyzed by applying series laws to the series portion and parallel laws to the parallel portion of the circuit.

40-11 Describe DC and AC and Kirchhoff’s current law.

• There are two fundamental types of current flow: DC and AC.
• DC is produced by a battery. It maintains the same positive and negative polarity; hence the current flows only in one direction.
• AC current is the type of current supplied to homes. It rapidly reverses or alternates its polarity; hence the current flows back and forth within the circuit.
• AC is produced in a sine wave; that is, it gradually increases in one direction, then similarly drops to zero before increasing in the other direction and returning to zero.
• This entire cycle can occur many times a second, with home supply usually being 50 to 60 cycles per second.
• Cycles per second or frequency is also called hertz.
• Kirchhoff’s current law is used to understand how parallel circuits work and states that the current entering any junction is equal to the sum of current flowing out of the junction.

40-12 Explain how to use electrical concepts to solve problems.

• If the amps in a circuit are lower than they should be, the two possible causes may be that the voltage is too low or the resistance is too high.
• The voltage may be too low if the charging system is not working, and the resistance may be too high if connections are dirty or loose.
• If the amps in a circuit are too high, it may be because the voltage is too high, or the resistance is too low.
• The voltage can be too high if the charging system puts out too much voltage, and the resistance can be too low due to a short circuit.
• In many cases, observing the current flow can help determine the type of fault to look for, and this can sometimes be evident without using a meter, such as when a light is dim.
• Measuring the resistance of an electric device will indicate whether a high resistance or open circuit condition is present, and comparing the readings with the specifications will indicate if the resistance is correct.

Post-Lecture

This section contains various student-centered end-of-chapter activities designed as enhancements to the instructor’s presentation. As time permits, these activities may be presented in class. They are also designed to be used as homework activities.

1. Direct students to read and individually answer the question sets located in the Wrap-Up section at the end of each chapter. Allow approximately 10–20 minutes for this part of the activity.
2. Facilitate a class review and discussion of the answers, allowing students to correct responses as may be needed. Use the answers noted in the Answer Key to assist in building this review.
3. You may wish to ask students to complete this activity on their own and turn in their answers on a separate piece of paper.

Review Questions

This question set is designed to assist students in understanding the chapter content by asking knowledge-based comprehension questions.

1. Understanding the behavior of electricity can be more difficult than understanding other concepts, primarily because it cannot be:

2. Materials that are composed of atoms that easily give up and accept electrons are known as:

3. What happens to the resistance of a conductor as its length increases?
   1. It increases.
   2. It decreases.
   3. It stays the same.
   4. It depends on the material.

4. What is the term for electrical flow?
   1. Voltage
   2. Amperage
   3. Resistance
   4. Conductance

5. What best describes electromagnetic induction?
   1. Electricity that is created inside of special cells during sunlight.
   2. Electricity that is created when a crystal is distorted or under mechanical stress.
   3. Electricity that is formed by two dissimilar metals submerged in electrolyte.
   4. Electricity that is created when a wire passes through a magnetic field.

6. A circuit has 12 volts, and 4 ohms of resistance. What is the amperage according to the Ohm’s law calculation?
   1. 12 amps
   2. 8 amps
   3. 3 amps
   4. 48 amps

7. If a load is using 10 amps at 12 volts, how many watts of power is this according to the Watt’s law calculation?
   1. 22 watts
   2. 100 watts
   3. 120 watts
   4. 180 watts

8. If a series circuit has two loads, each being 8 ohms, what is the combined resistance of the loads?
   1. 4 ohms
   2. 8 ohms
   3. 16 ohms
   4. 64 ohms

9. If a circuit has two loads in parallel, each being 4 ohms, what is the resistance of the loads in the circuit?
   1. .5 ohms
   2. 2 ohms
   3. 8 ohms
   4. 16 ohms

10. If a lightbulb is too dim, what is the most likely cause?
    1. Circuit voltage too high
    2. Circuit resistance too low
    3. Circuit amperage too high
    4. Circuit resistance too high

ASE Technician A/Technician B Style Questions

This question set is designed to assist students in gaining a further understanding of and familiarity with ASE Technician A/Technician B questions.

1. Electrical fundamentals are being discussed. Technician A states that amperage is a measure of electrical pressure. Technician B states that resistance is measured in ohms.
   1. Technician A
   2. Technician B
   3. Both A and B
   4. Neither A nor B

2. The laws of electricity are being discussed. Technician A states that as a conductor heats up, its resistance increases. Technician B states that resistors are designed to extract energy from the current flow as it passes through the resistor. Who is correct?
   1. Technician A
   2. Technician B
   3. Both A and B
   4. Neither A nor B

3. Measuring electricity and electrical components are being discussed. Technician A states that a voltmeter is used to measure current flow. Technician B states that an ohmmeter is used to measure resistance. Who is correct?
   1. Technician A
   2. Technician B
   3. Both A and B
   4. Neither A nor B

4. Electricity being applied to modern vehicles is being discussed. Technician A states that some vehicles use photovoltaic technology to sense daylight. Technician B states that electromagnetic induction is rarely used on modern vehicles. Who is correct?
   1. Technician A
   2. Technician B
   3. Both A and B
   4. Neither A nor B

5. LEDs are being discussed. Technician A states that LEDs create much more heat compared to traditional bulbs. Technician B states that LEDs are replacing traditional bulbs in more and more new vehicles. Who is correct?
   1. Technician A
   2. Technician B
   3. Both A and B
   4. Neither A nor B

6. An electrical circuit and Ohm’s law are being discussed. Technician A states that if voltage increases, and resistance stays the same, amperage will decrease. Technician B states that if resistance decreases and voltage stays the same, amperage will decrease. Who is correct?
   1. Technician A
   2. Technician B
   3. Both A and B
   4. Neither A nor B

7. An electrical circuit and Watt’s law are being disused. Technician A states that if amperage increases and voltage stays the same, the power will increase. Technician B states that if voltage goes up, and amperage goes up, the power will increase. Who is correct?
   1. Technician A
   2. Technician B
   3. Both A and B
   4. Neither A nor B

8. An electrical circuit is being discussed. Technician A states that if one load is added in series, the total resistance decreases. Technician B states that the voltage applied to a series circuit will be shared between each of the loads. Who is correct?
   1. Technician A
   2. Technician B
   3. Both A and B
   4. Neither A nor B

9. Electrical current is being discussed. Technician A states that AC is normally stored in a battery. Technician B states that hertz is the number of times per second an AC waveform cycles between positive and negative. Who is correct?
   1. Technician A
   2. Technician B
   3. Both A and B
   4. Neither A nor B

10. An electrical circuit is being discussed. Technician A states that if resistance is added, the current will decrease. Technician B states that if voltage is decreased, amperage would increase. Who is correct?
    1. Technician A
    2. Technician B
    3. Both A and B
    4. Neither A nor B

Assignments

• Review all materials from this chapter and be prepared for a chapter quiz to be administered (date to be determined by instructor).
• Direct students to read the next chapter in Fundamentals of Automotive Maintenance and Light Repair, Second Edition as listed on your syllabus to prepare for the next class session.