2. Automotive Technology Practicum Period 2-3 (Kingsville Independent School District) //www.kingsvilleisd.com/apps/classes/1061077/assignments/ Class Name: 2. Automotive Technology Practicum Period 2-3 Instructor(s): Secundino Garza, A.A.S, B.S, M.S., A.S.E. en-us SchoolSitePro <![CDATA[Due: 10/11/2025]]> //www.kingsvilleisd.com/homeworkItem10727476 //www.kingsvilleisd.com/apps/classes/1061077/assignments/

Chapter 47

Principles of Heating and Air-Conditioning Systems

 

Learning Objectives

After reading this chapter, you will be able to:

  • 47-01 Describe the history of air conditioning and the required licensure.
  • 47-02 Explain the physics that allows air conditioning.
  • 47-03 Explain the qualities of refrigerant and the refrigerant cycle.
  • 47-04 Explain the main air-conditioning components and their operation.
  • 47-05 Explain the types of refrigerant and refrigerant oils.
  • 47-06 Describe the heating and ventilation system operation.
  • 47-07 Describe the operation of the defroster and blower motor operation.
  • 47-08 Performance test and check HVAC system.

 

ASE Education Foundation Tasks

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

  • VIIA2 Identify heating, ventilation and air conditioning (HVAC) components and configuration.
  • VIIB1 Inspect and replace A/C compressor drive belts, pulleys, and tensioners; visually inspect A/C components for signs of leaks; determine necessary action.
  • VIIB3 Inspect A/C condenser for airflow restrictions; determine necessary action.
  • VIID1 Inspect A/C-heater ducts, doors, hoses, cabin filters, and outlets; determine necessary action.
  • VIID2 Identify the source of A/C system odors.

 

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 heating and air-conditioning 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 heating and air-conditioning systems.

 

Lecture

47-01 Describe the history of air conditioning and the required licensure.

 

  • In 1902, Willis Carrier invented and patented the first electric air conditioner.
  • In 1928, a research division of General Motors produced chlorofluorocarbons (CFCs) that made it possible for air-conditioning systems to be used by consumers with no apparent harm.
  • In 1939, Packard introduced the first automotive air-conditioning system, which was an add-on luxury unit.
  • Automotive air-conditioning service technicians need to have a special license granted after passing the 609 test, which is a self-study course.
  • The 609 license also allows the technician to purchase a few select refrigerants, such as R-12, R-134a, and HFO 1234.

47-02 Explain the physics that allows air conditioning.

 

  • The HVAC system removes excess heat from the passenger compartment and transfers it to the outside air through a series of thermal and chemical transformations.
  • The HVAC system is governed by the principles of physics.
  • Convection currents from the heated air in the passenger compartment are pushed through an evaporator core filled with refrigerant; the metal coils of the evaporator then transfer the heat by conduction to the refrigerant.
  • The refrigerant is then circulated by the compressor and carried to the condenser where conduction and convection dissipate the heat to the surrounding air.
  • The changing of state in liquids and gases, referred to as vaporizing and condensing, is the basis of air-conditioning.
  • Air conditioning uses the process of evaporating a liquid to absorb a large amount of heat energy.

47-03 Explain the qualities of refrigerant and the refrigerant cycle.

 

  • The refrigerant must have a boiling point well below freezing so that its boiling and condensing points can be modified by changing pressure.
  • The super-low boiling point of most refrigerants allows the system to control the vaporization and condensation points of the refrigerant at normal ambient temperatures.
  • Starting at the compressor, a low-pressure gas is compressed into a high-pressure gas. It is pumped into the condenser located in front of the vehicle radiator.
  • The gaseous refrigerant is cooled by the air passing through the condenser and leaves the condenser as a high-pressure liquid; it then travels through a small orifice that reduces the pressure of the refrigerant.
  • The low-pressure liquid leaves the metering device and travels into the evaporator in the passenger compartment where a fan blows warm to hot cabin air across the fins, which heats the refrigerant until it boils.
  • As it boils, it absorbs heat from the air; the liquid refrigerant is then transformed back into a gas and the gaseous refrigerant travels back to the compressor to start the cycle over.

47-04 Explain the main air-conditioning components and their operation.

 

  • Each HVAC system uses refrigerant and four major components.
  • The components are the compressor, condenser, restriction, and evaporator.
  • The air conditioner is a closed-loop system in which the refrigerant continues to cycle through the system, changing pressure and state to complete the task of cooling the cabin.
  • The air-conditioning cycle starts with the compressor; the compressor changes a low-pressure refrigerant gas to a high-pressure gas and provides the needed refrigerant movement in the system information.
  • The condenser transforms gas to liquid on the high side of the system.
  • Lowering the pressure occurs by flowing a liquid through a restriction; the restriction lowers the pressure according to the Bernoulli principle.
  • The evaporator transforms low-pressure liquid to a low-pressure gas.

47-05 Explain the types of refrigerant and refrigerant oils.

 

  • The three most common types of refrigerants used in automotive applications are R-12, R-134a, or HFO-1234yf.
  • Dichlorodifluoromethane (R-12) was the first common refrigerant to be used in automotive air conditioners; it has a boiling point of -21.8°F and is nonflammable, nontoxic, and stable at all temperatures.
  • R-12 was found to be one of the leading causes of the depletion of the ozone layer and was outlawed for new vehicle installation.
  • Tetrafluoroethane (R-134a) was the replacement for R-12; it is a hydrofluorocarbon having a boiling point of -15.3°F. It is nonflammable and safe for automotive air conditioners, but it is a major contributor to greenhouse gases.
  • Tetrafluoropropene (HFO-1234yf) is the latest refrigerant for mobile air-conditioning systems; it has a greatly reduced global warming potential (GWP) of 4 compared with a GWP of 1430 for R-134a refrigerant; it has a boiling point of -20.2°F and is slightly flammable.
  • The old refrigerant R-12 used mineral oil, R-134a uses a PAG oil, and either PAG or POE oil is recommended for use with HFO-1234yf, depending on the system.

47-06 Describe the heating and ventilation system operation.

 

  • As the engine heats up from the process of burning fuel to create power, the coolant in the engine is also heated; the heat from the hot coolant opens the thermostat, and the water pump pushes the coolant into the radiator.
  • Airflow from the vehicle moving and/or from the cooling fans passes through the radiator, and heat is transferred to the air, warming the air and reducing the temperature of the coolant. The coolant is then cycled back through the engine to restart the process.
  • Heated coolant is also pumped to a heater core; the blower motor causes air to flow through the heater core and is warmed, and the heated air is directed into the passenger compartment.
  • To adjust the amount of heat delivered to the cabin, some heating systems use a control valve on the inlet of the heater. Others use a blend door to control air bypassing the heater core.

47-07 Describe the operation of the defroster and blower motor operation.

 

  • In the defrost mode, air passes through the evaporator and the heater core and produces dry, heated air; hot, dry air from the defrost duct hits the windshield, and the moisture from the glass is quickly drawn into the air.
  • Blower motors determine the rate of airflow out of the vents.
  • The “squirrel cage” attached to the spinning shaft of the motor is a plastic cage with fins that pull or push air.
  • Placing the blower before the evaporator pushes air through the evaporator and heater core in the box.
  • The resistor pack or resistor block is a common blower motor control that uses resistors in series to regulate the speed of the fan; the lowest speed passes the current through several resistors, and the highest speed uses no resistors, so the motor has full current flow.

47-08 Performance test and check HVAC system.

 

  • Performance testing is the term used to describe the standard air-conditioning testing process.
  • When performance testing the air-conditioning system, make sure to have all of the controls at the maximum settings.
  • Performance testing of HVAC systems includes measuring the duct air temperature, checks for abnormal noise, condenser inspection for airflow restrictions, evaporator housing water drain inspection, and elimination of air-conditioning system odors.

 

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 year was the first automotive air-conditioning system offered on a new vehicle?
    1. 1931
    2. 1939
    3. 1958
    4. 1976

 

  1. Which certification is a technician required to hold in order to legally handle refrigerant in a vehicle?
    1. 609
    2. R-22
    3. ASE A7
    4. MVAC

 

  1. Which type of heat transfer occurs when cold air surrounds your body and cools it?
    1. Conduction
    2. Convention
    3. Convection
    4. Radiation

 

  1. At atmospheric pressure, what temperature does R-134a boil at?
    1. –15°F
    2. 32°F
    3. 100°C
    4. 212°F

 

  1. In refrigeration, how can we force refrigerant to evaporate?
    1. By compressing it
    2. By speeding it up
    3. By slowing it down
    4. By reducing its pressure

 

  1. In an air-conditioning system, which component receives refrigerant as a low-pressure liquid and changes it to a low-pressure gas, and as a result, absorbs surrounding heat?
    1. The condenser
    2. The compressor
    3. The evaporator
    4. The accumulator

 

  1. In an air-conditioning system, which device changes the high-pressure gas refrigerant into a high-pressure liquid after giving off its stored heat?
    1. The evaporator
    2. The condenser
    3. The accumulator
    4. The orifice

 

  1. R-12 refrigerant was found to be a leading cause of ozone layer depletion; what is the latest refrigerant used by manu­facturers that has the least effect on the ozone layer?
    1. Freon
    2. R-134a
    3. Tetraflouroethane
    4. HFO-1234yf

 

  1. In the HVAC system, which component heats the sur­rounding air for passenger comfort when the system is set to a warm temperature?
    1. The thermostat
    2. The radiator
    3. The heater core
    4. The evaporator

 

  1. When performance testing an AC system on the max cool setting, how would a technician know the acceptable tem­perature range?
    1. It should be between 39°F and 45°F on a hot day.
    2. They should compare it to another vehicle temperature that day.
    3. They should ask the customer what the temperature was.
    4. They should refer to the diagnostic chart in service information.

 

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. Refrigerant handling certification is being discussed. Technician A states that a technician can obtain the 609 certification from ASE. Technician B states that a techni­cian can obtain the 609 certification from MACS. Who is correct?
    1. Technician A
    2. Technician B
    3. Both A and B
    4. Neither A nor B

 

  1. Air-conditioning principles are being discussed. Techni­cian A states that heat always travels from hot to cold. Technician B states that convection is heat that travels through solids. Who is correct?
    1. Technician A
    2. Technician B
    3. Both A and B
    4. Neither A nor B

 

  1. Air-conditioning fundamentals are being discussed. Technician A states that the sun heating your body through a windshield on a sunny day is called radiant heat. Technician B states that heat that cannot be felt or measured is called latent heat. Who is correct?
    1. Technician A
    2. Technician B
    3. Both A and B
    4. Neither A nor B

 

  1. Principles of AC are being discussed. Technician A states that if R-134a is pressurized to 15 psi, it will boil at just over 32°F. Technician B states that as R-134a boils in the AC system, it gives off heat to air surrounding it. Who is correct?
    1. Technician A
    2. Technician B
    3. Both A and B
    4. Neither A nor B

 

  1. The states of refrigerant are being discussed. Technician A states that when a refrigerant changes from a gas to a liquid, it absorbs heat. Technician B states that when a refriger­ant changes from a liquid to a gas, it gives off heat. Who is correct?
    1. Technician A
    2. Technician B
    3. Both A and B
    4. Neither A nor B

 

  1. Air-conditioning components are being discussed. Technician A states that a restriction device can be a fixed orifice or a thermal expansion valve. Technician B states that the purpose of the compressor is to circulate refrigerant, and with the help of a restriction, control the refrigerant pressure. Who is correct?
    1. Technician A
    2. Technician B
    3. Both A and B
    4. Neither A nor B

 

  1. Refrigerant types are being discussed. Technician A states that R-134a is being phased out because it was recently found to be a major contributor to greenhouse gases. Technician B states that HFO-1234yf is non-flammable. Who is correct?
    1. Technician A
    2. Technician B
    3. Both A and B
    4. Neither A nor B

 

  1. An HVAC system is being discussed. Technician A states that on most vehicles, the MAX cold setting will pull air from the outside to provide maximum cooling. Technician B states that on some vehicles, a heater control valve blocks coolant from entering the heater core unless the heater is turned on. Who is correct?
    1. Technician A
    2. Technician B
    3. Both A and B
    4. Neither A nor B

 

  1. An HVAC system is being discussed. Technician A states that on some vehicles, the AC may be turned on automatically when defrosting the windshield since it dries the air. Technician B states that many vehicles use a blower mo­tor resistor pack to control blower motor speeds. Who is correct?
    1. Technician A
    2. Technician B
    3. Both A and B
    4. Neither A nor B

 

  1. An HVAC system is being discussed. Technician A states that water dripping from the center of the vehicle on a humid day with the AC on may be normal. Technician B states that some manufacturers are using charcoal cabin filters which trap odors and airborne pollutants before they enter the cabin. 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.

]]> Tue, 07 Oct 2025 06:49:40 PDT <![CDATA[Due: 10/04/2025]]> //www.kingsvilleisd.com/homeworkItem10691581 //www.kingsvilleisd.com/apps/classes/1061077/assignments/

Chapter 47

Principles of Heating and Air-Conditioning Systems

 

Learning Objectives

After reading this chapter, you will be able to:

  • 47-01 Describe the history of air conditioning and the required licensure.
  • 47-02 Explain the physics that allows air conditioning.
  • 47-03 Explain the qualities of refrigerant and the refrigerant cycle.
  • 47-04 Explain the main air-conditioning components and their operation.
  • 47-05 Explain the types of refrigerant and refrigerant oils.
  • 47-06 Describe the heating and ventilation system operation.
  • 47-07 Describe the operation of the defroster and blower motor operation.
  • 47-08 Performance test and check HVAC system.

 

ASE Education Foundation Tasks

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

  • VIIA2 Identify heating, ventilation and air conditioning (HVAC) components and configuration.
  • VIIB1 Inspect and replace A/C compressor drive belts, pulleys, and tensioners; visually inspect A/C components for signs of leaks; determine necessary action.
  • VIIB3 Inspect A/C condenser for airflow restrictions; determine necessary action.
  • VIID1 Inspect A/C-heater ducts, doors, hoses, cabin filters, and outlets; determine necessary action.
  • VIID2 Identify the source of A/C system odors.

 

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 heating and air-conditioning 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 heating and air-conditioning systems.

 

Lecture

47-01 Describe the history of air conditioning and the required licensure.

 

  • In 1902, Willis Carrier invented and patented the first electric air conditioner.
  • In 1928, a research division of General Motors produced chlorofluorocarbons (CFCs) that made it possible for air-conditioning systems to be used by consumers with no apparent harm.
  • In 1939, Packard introduced the first automotive air-conditioning system, which was an add-on luxury unit.
  • Automotive air-conditioning service technicians need to have a special license granted after passing the 609 test, which is a self-study course.
  • The 609 license also allows the technician to purchase a few select refrigerants, such as R-12, R-134a, and HFO 1234.

47-02 Explain the physics that allows air conditioning.

 

  • The HVAC system removes excess heat from the passenger compartment and transfers it to the outside air through a series of thermal and chemical transformations.
  • The HVAC system is governed by the principles of physics.
  • Convection currents from the heated air in the passenger compartment are pushed through an evaporator core filled with refrigerant; the metal coils of the evaporator then transfer the heat by conduction to the refrigerant.
  • The refrigerant is then circulated by the compressor and carried to the condenser where conduction and convection dissipate the heat to the surrounding air.
  • The changing of state in liquids and gases, referred to as vaporizing and condensing, is the basis of air-conditioning.
  • Air conditioning uses the process of evaporating a liquid to absorb a large amount of heat energy.

47-03 Explain the qualities of refrigerant and the refrigerant cycle.

 

  • The refrigerant must have a boiling point well below freezing so that its boiling and condensing points can be modified by changing pressure.
  • The super-low boiling point of most refrigerants allows the system to control the vaporization and condensation points of the refrigerant at normal ambient temperatures.
  • Starting at the compressor, a low-pressure gas is compressed into a high-pressure gas. It is pumped into the condenser located in front of the vehicle radiator.
  • The gaseous refrigerant is cooled by the air passing through the condenser and leaves the condenser as a high-pressure liquid; it then travels through a small orifice that reduces the pressure of the refrigerant.
  • The low-pressure liquid leaves the metering device and travels into the evaporator in the passenger compartment where a fan blows warm to hot cabin air across the fins, which heats the refrigerant until it boils.
  • As it boils, it absorbs heat from the air; the liquid refrigerant is then transformed back into a gas and the gaseous refrigerant travels back to the compressor to start the cycle over.

47-04 Explain the main air-conditioning components and their operation.

 

  • Each HVAC system uses refrigerant and four major components.
  • The components are the compressor, condenser, restriction, and evaporator.
  • The air conditioner is a closed-loop system in which the refrigerant continues to cycle through the system, changing pressure and state to complete the task of cooling the cabin.
  • The air-conditioning cycle starts with the compressor; the compressor changes a low-pressure refrigerant gas to a high-pressure gas and provides the needed refrigerant movement in the system information.
  • The condenser transforms gas to liquid on the high side of the system.
  • Lowering the pressure occurs by flowing a liquid through a restriction; the restriction lowers the pressure according to the Bernoulli principle.
  • The evaporator transforms low-pressure liquid to a low-pressure gas.

47-05 Explain the types of refrigerant and refrigerant oils.

 

  • The three most common types of refrigerants used in automotive applications are R-12, R-134a, or HFO-1234yf.
  • Dichlorodifluoromethane (R-12) was the first common refrigerant to be used in automotive air conditioners; it has a boiling point of -21.8°F and is nonflammable, nontoxic, and stable at all temperatures.
  • R-12 was found to be one of the leading causes of the depletion of the ozone layer and was outlawed for new vehicle installation.
  • Tetrafluoroethane (R-134a) was the replacement for R-12; it is a hydrofluorocarbon having a boiling point of -15.3°F. It is nonflammable and safe for automotive air conditioners, but it is a major contributor to greenhouse gases.
  • Tetrafluoropropene (HFO-1234yf) is the latest refrigerant for mobile air-conditioning systems; it has a greatly reduced global warming potential (GWP) of 4 compared with a GWP of 1430 for R-134a refrigerant; it has a boiling point of -20.2°F and is slightly flammable.
  • The old refrigerant R-12 used mineral oil, R-134a uses a PAG oil, and either PAG or POE oil is recommended for use with HFO-1234yf, depending on the system.

47-06 Describe the heating and ventilation system operation.

 

  • As the engine heats up from the process of burning fuel to create power, the coolant in the engine is also heated; the heat from the hot coolant opens the thermostat, and the water pump pushes the coolant into the radiator.
  • Airflow from the vehicle moving and/or from the cooling fans passes through the radiator, and heat is transferred to the air, warming the air and reducing the temperature of the coolant. The coolant is then cycled back through the engine to restart the process.
  • Heated coolant is also pumped to a heater core; the blower motor causes air to flow through the heater core and is warmed, and the heated air is directed into the passenger compartment.
  • To adjust the amount of heat delivered to the cabin, some heating systems use a control valve on the inlet of the heater. Others use a blend door to control air bypassing the heater core.

47-07 Describe the operation of the defroster and blower motor operation.

 

  • In the defrost mode, air passes through the evaporator and the heater core and produces dry, heated air; hot, dry air from the defrost duct hits the windshield, and the moisture from the glass is quickly drawn into the air.
  • Blower motors determine the rate of airflow out of the vents.
  • The “squirrel cage” attached to the spinning shaft of the motor is a plastic cage with fins that pull or push air.
  • Placing the blower before the evaporator pushes air through the evaporator and heater core in the box.
  • The resistor pack or resistor block is a common blower motor control that uses resistors in series to regulate the speed of the fan; the lowest speed passes the current through several resistors, and the highest speed uses no resistors, so the motor has full current flow.

47-08 Performance test and check HVAC system.

 

  • Performance testing is the term used to describe the standard air-conditioning testing process.
  • When performance testing the air-conditioning system, make sure to have all of the controls at the maximum settings.
  • Performance testing of HVAC systems includes measuring the duct air temperature, checks for abnormal noise, condenser inspection for airflow restrictions, evaporator housing water drain inspection, and elimination of air-conditioning system odors.

 

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 year was the first automotive air-conditioning system offered on a new vehicle?
    1. 1931
    2. 1939
    3. 1958
    4. 1976

 

  1. Which certification is a technician required to hold in order to legally handle refrigerant in a vehicle?
    1. 609
    2. R-22
    3. ASE A7
    4. MVAC

 

  1. Which type of heat transfer occurs when cold air surrounds your body and cools it?
    1. Conduction
    2. Convention
    3. Convection
    4. Radiation

 

  1. At atmospheric pressure, what temperature does R-134a boil at?
    1. –15°F
    2. 32°F
    3. 100°C
    4. 212°F

 

  1. In refrigeration, how can we force refrigerant to evaporate?
    1. By compressing it
    2. By speeding it up
    3. By slowing it down
    4. By reducing its pressure

 

  1. In an air-conditioning system, which component receives refrigerant as a low-pressure liquid and changes it to a low-pressure gas, and as a result, absorbs surrounding heat?
    1. The condenser
    2. The compressor
    3. The evaporator
    4. The accumulator

 

  1. In an air-conditioning system, which device changes the high-pressure gas refrigerant into a high-pressure liquid after giving off its stored heat?
    1. The evaporator
    2. The condenser
    3. The accumulator
    4. The orifice

 

  1. R-12 refrigerant was found to be a leading cause of ozone layer depletion; what is the latest refrigerant used by manu­facturers that has the least effect on the ozone layer?
    1. Freon
    2. R-134a
    3. Tetraflouroethane
    4. HFO-1234yf

 

  1. In the HVAC system, which component heats the sur­rounding air for passenger comfort when the system is set to a warm temperature?
    1. The thermostat
    2. The radiator
    3. The heater core
    4. The evaporator

 

  1. When performance testing an AC system on the max cool setting, how would a technician know the acceptable tem­perature range?
    1. It should be between 39°F and 45°F on a hot day.
    2. They should compare it to another vehicle temperature that day.
    3. They should ask the customer what the temperature was.
    4. They should refer to the diagnostic chart in service information.

 

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. Refrigerant handling certification is being discussed. Technician A states that a technician can obtain the 609 certification from ASE. Technician B states that a techni­cian can obtain the 609 certification from MACS. Who is correct?
    1. Technician A
    2. Technician B
    3. Both A and B
    4. Neither A nor B

 

  1. Air-conditioning principles are being discussed. Techni­cian A states that heat always travels from hot to cold. Technician B states that convection is heat that travels through solids. Who is correct?
    1. Technician A
    2. Technician B
    3. Both A and B
    4. Neither A nor B

 

  1. Air-conditioning fundamentals are being discussed. Technician A states that the sun heating your body through a windshield on a sunny day is called radiant heat. Technician B states that heat that cannot be felt or measured is called latent heat. Who is correct?
    1. Technician A
    2. Technician B
    3. Both A and B
    4. Neither A nor B

 

  1. Principles of AC are being discussed. Technician A states that if R-134a is pressurized to 15 psi, it will boil at just over 32°F. Technician B states that as R-134a boils in the AC system, it gives off heat to air surrounding it. Who is correct?
    1. Technician A
    2. Technician B
    3. Both A and B
    4. Neither A nor B

 

  1. The states of refrigerant are being discussed. Technician A states that when a refrigerant changes from a gas to a liquid, it absorbs heat. Technician B states that when a refriger­ant changes from a liquid to a gas, it gives off heat. Who is correct?
    1. Technician A
    2. Technician B
    3. Both A and B
    4. Neither A nor B

 

  1. Air-conditioning components are being discussed. Technician A states that a restriction device can be a fixed orifice or a thermal expansion valve. Technician B states that the purpose of the compressor is to circulate refrigerant, and with the help of a restriction, control the refrigerant pressure. Who is correct?
    1. Technician A
    2. Technician B
    3. Both A and B
    4. Neither A nor B

 

  1. Refrigerant types are being discussed. Technician A states that R-134a is being phased out because it was recently found to be a major contributor to greenhouse gases. Technician B states that HFO-1234yf is non-flammable. Who is correct?
    1. Technician A
    2. Technician B
    3. Both A and B
    4. Neither A nor B

 

  1. An HVAC system is being discussed. Technician A states that on most vehicles, the MAX cold setting will pull air from the outside to provide maximum cooling. Technician B states that on some vehicles, a heater control valve blocks coolant from entering the heater core unless the heater is turned on. Who is correct?
    1. Technician A
    2. Technician B
    3. Both A and B
    4. Neither A nor B

 

  1. An HVAC system is being discussed. Technician A states that on some vehicles, the AC may be turned on automatically when defrosting the windshield since it dries the air. Technician B states that many vehicles use a blower mo­tor resistor pack to control blower motor speeds. Who is correct?
    1. Technician A
    2. Technician B
    3. Both A and B
    4. Neither A nor B

 

  1. An HVAC system is being discussed. Technician A states that water dripping from the center of the vehicle on a humid day with the AC on may be normal. Technician B states that some manufacturers are using charcoal cabin filters which trap odors and airborne pollutants before they enter the cabin. 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.

]]> Tue, 23 Sep 2025 12:25:29 PDT <![CDATA[Due: 09/27/2025]]> //www.kingsvilleisd.com/homeworkItem10688798 //www.kingsvilleisd.com/apps/classes/1061077/assignments/

Chapter 47

Principles of Heating and Air-Conditioning Systems

 

Learning Objectives

After reading this chapter, you will be able to:

  • 47-01 Describe the history of air conditioning and the required licensure.
  • 47-02 Explain the physics that allows air conditioning.
  • 47-03 Explain the qualities of refrigerant and the refrigerant cycle.
  • 47-04 Explain the main air-conditioning components and their operation.
  • 47-05 Explain the types of refrigerant and refrigerant oils.
  • 47-06 Describe the heating and ventilation system operation.
  • 47-07 Describe the operation of the defroster and blower motor operation.
  • 47-08 Performance test and check HVAC system.

 

ASE Education Foundation Tasks

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

  • VIIA2 Identify heating, ventilation and air conditioning (HVAC) components and configuration.
  • VIIB1 Inspect and replace A/C compressor drive belts, pulleys, and tensioners; visually inspect A/C components for signs of leaks; determine necessary action.
  • VIIB3 Inspect A/C condenser for airflow restrictions; determine necessary action.
  • VIID1 Inspect A/C-heater ducts, doors, hoses, cabin filters, and outlets; determine necessary action.
  • VIID2 Identify the source of A/C system odors.

 

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 heating and air-conditioning 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 heating and air-conditioning systems.

 

Lecture

47-01 Describe the history of air conditioning and the required licensure.

 

  • In 1902, Willis Carrier invented and patented the first electric air conditioner.
  • In 1928, a research division of General Motors produced chlorofluorocarbons (CFCs) that made it possible for air-conditioning systems to be used by consumers with no apparent harm.
  • In 1939, Packard introduced the first automotive air-conditioning system, which was an add-on luxury unit.
  • Automotive air-conditioning service technicians need to have a special license granted after passing the 609 test, which is a self-study course.
  • The 609 license also allows the technician to purchase a few select refrigerants, such as R-12, R-134a, and HFO 1234.

47-02 Explain the physics that allows air conditioning.

 

  • The HVAC system removes excess heat from the passenger compartment and transfers it to the outside air through a series of thermal and chemical transformations.
  • The HVAC system is governed by the principles of physics.
  • Convection currents from the heated air in the passenger compartment are pushed through an evaporator core filled with refrigerant; the metal coils of the evaporator then transfer the heat by conduction to the refrigerant.
  • The refrigerant is then circulated by the compressor and carried to the condenser where conduction and convection dissipate the heat to the surrounding air.
  • The changing of state in liquids and gases, referred to as vaporizing and condensing, is the basis of air-conditioning.
  • Air conditioning uses the process of evaporating a liquid to absorb a large amount of heat energy.

47-03 Explain the qualities of refrigerant and the refrigerant cycle.

 

  • The refrigerant must have a boiling point well below freezing so that its boiling and condensing points can be modified by changing pressure.
  • The super-low boiling point of most refrigerants allows the system to control the vaporization and condensation points of the refrigerant at normal ambient temperatures.
  • Starting at the compressor, a low-pressure gas is compressed into a high-pressure gas. It is pumped into the condenser located in front of the vehicle radiator.
  • The gaseous refrigerant is cooled by the air passing through the condenser and leaves the condenser as a high-pressure liquid; it then travels through a small orifice that reduces the pressure of the refrigerant.
  • The low-pressure liquid leaves the metering device and travels into the evaporator in the passenger compartment where a fan blows warm to hot cabin air across the fins, which heats the refrigerant until it boils.
  • As it boils, it absorbs heat from the air; the liquid refrigerant is then transformed back into a gas and the gaseous refrigerant travels back to the compressor to start the cycle over.

47-04 Explain the main air-conditioning components and their operation.

 

  • Each HVAC system uses refrigerant and four major components.
  • The components are the compressor, condenser, restriction, and evaporator.
  • The air conditioner is a closed-loop system in which the refrigerant continues to cycle through the system, changing pressure and state to complete the task of cooling the cabin.
  • The air-conditioning cycle starts with the compressor; the compressor changes a low-pressure refrigerant gas to a high-pressure gas and provides the needed refrigerant movement in the system information.
  • The condenser transforms gas to liquid on the high side of the system.
  • Lowering the pressure occurs by flowing a liquid through a restriction; the restriction lowers the pressure according to the Bernoulli principle.
  • The evaporator transforms low-pressure liquid to a low-pressure gas.

47-05 Explain the types of refrigerant and refrigerant oils.

 

  • The three most common types of refrigerants used in automotive applications are R-12, R-134a, or HFO-1234yf.
  • Dichlorodifluoromethane (R-12) was the first common refrigerant to be used in automotive air conditioners; it has a boiling point of -21.8°F and is nonflammable, nontoxic, and stable at all temperatures.
  • R-12 was found to be one of the leading causes of the depletion of the ozone layer and was outlawed for new vehicle installation.
  • Tetrafluoroethane (R-134a) was the replacement for R-12; it is a hydrofluorocarbon having a boiling point of -15.3°F. It is nonflammable and safe for automotive air conditioners, but it is a major contributor to greenhouse gases.
  • Tetrafluoropropene (HFO-1234yf) is the latest refrigerant for mobile air-conditioning systems; it has a greatly reduced global warming potential (GWP) of 4 compared with a GWP of 1430 for R-134a refrigerant; it has a boiling point of -20.2°F and is slightly flammable.
  • The old refrigerant R-12 used mineral oil, R-134a uses a PAG oil, and either PAG or POE oil is recommended for use with HFO-1234yf, depending on the system.

47-06 Describe the heating and ventilation system operation.

 

  • As the engine heats up from the process of burning fuel to create power, the coolant in the engine is also heated; the heat from the hot coolant opens the thermostat, and the water pump pushes the coolant into the radiator.
  • Airflow from the vehicle moving and/or from the cooling fans passes through the radiator, and heat is transferred to the air, warming the air and reducing the temperature of the coolant. The coolant is then cycled back through the engine to restart the process.
  • Heated coolant is also pumped to a heater core; the blower motor causes air to flow through the heater core and is warmed, and the heated air is directed into the passenger compartment.
  • To adjust the amount of heat delivered to the cabin, some heating systems use a control valve on the inlet of the heater. Others use a blend door to control air bypassing the heater core.

47-07 Describe the operation of the defroster and blower motor operation.

 

  • In the defrost mode, air passes through the evaporator and the heater core and produces dry, heated air; hot, dry air from the defrost duct hits the windshield, and the moisture from the glass is quickly drawn into the air.
  • Blower motors determine the rate of airflow out of the vents.
  • The “squirrel cage” attached to the spinning shaft of the motor is a plastic cage with fins that pull or push air.
  • Placing the blower before the evaporator pushes air through the evaporator and heater core in the box.
  • The resistor pack or resistor block is a common blower motor control that uses resistors in series to regulate the speed of the fan; the lowest speed passes the current through several resistors, and the highest speed uses no resistors, so the motor has full current flow.

47-08 Performance test and check HVAC system.

 

  • Performance testing is the term used to describe the standard air-conditioning testing process.
  • When performance testing the air-conditioning system, make sure to have all of the controls at the maximum settings.
  • Performance testing of HVAC systems includes measuring the duct air temperature, checks for abnormal noise, condenser inspection for airflow restrictions, evaporator housing water drain inspection, and elimination of air-conditioning system odors.

 

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 year was the first automotive air-conditioning system offered on a new vehicle?
    1. 1931
    2. 1939
    3. 1958
    4. 1976

 

  1. Which certification is a technician required to hold in order to legally handle refrigerant in a vehicle?
    1. 609
    2. R-22
    3. ASE A7
    4. MVAC

 

  1. Which type of heat transfer occurs when cold air surrounds your body and cools it?
    1. Conduction
    2. Convention
    3. Convection
    4. Radiation

 

  1. At atmospheric pressure, what temperature does R-134a boil at?
    1. –15°F
    2. 32°F
    3. 100°C
    4. 212°F

 

  1. In refrigeration, how can we force refrigerant to evaporate?
    1. By compressing it
    2. By speeding it up
    3. By slowing it down
    4. By reducing its pressure

 

  1. In an air-conditioning system, which component receives refrigerant as a low-pressure liquid and changes it to a low-pressure gas, and as a result, absorbs surrounding heat?
    1. The condenser
    2. The compressor
    3. The evaporator
    4. The accumulator

 

  1. In an air-conditioning system, which device changes the high-pressure gas refrigerant into a high-pressure liquid after giving off its stored heat?
    1. The evaporator
    2. The condenser
    3. The accumulator
    4. The orifice

 

  1. R-12 refrigerant was found to be a leading cause of ozone layer depletion; what is the latest refrigerant used by manu­facturers that has the least effect on the ozone layer?
    1. Freon
    2. R-134a
    3. Tetraflouroethane
    4. HFO-1234yf

 

  1. In the HVAC system, which component heats the sur­rounding air for passenger comfort when the system is set to a warm temperature?
    1. The thermostat
    2. The radiator
    3. The heater core
    4. The evaporator

 

  1. When performance testing an AC system on the max cool setting, how would a technician know the acceptable tem­perature range?
    1. It should be between 39°F and 45°F on a hot day.
    2. They should compare it to another vehicle temperature that day.
    3. They should ask the customer what the temperature was.
    4. They should refer to the diagnostic chart in service information.

 

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. Refrigerant handling certification is being discussed. Technician A states that a technician can obtain the 609 certification from ASE. Technician B states that a techni­cian can obtain the 609 certification from MACS. Who is correct?
    1. Technician A
    2. Technician B
    3. Both A and B
    4. Neither A nor B

 

  1. Air-conditioning principles are being discussed. Techni­cian A states that heat always travels from hot to cold. Technician B states that convection is heat that travels through solids. Who is correct?
    1. Technician A
    2. Technician B
    3. Both A and B
    4. Neither A nor B

 

  1. Air-conditioning fundamentals are being discussed. Technician A states that the sun heating your body through a windshield on a sunny day is called radiant heat. Technician B states that heat that cannot be felt or measured is called latent heat. Who is correct?
    1. Technician A
    2. Technician B
    3. Both A and B
    4. Neither A nor B

 

  1. Principles of AC are being discussed. Technician A states that if R-134a is pressurized to 15 psi, it will boil at just over 32°F. Technician B states that as R-134a boils in the AC system, it gives off heat to air surrounding it. Who is correct?
    1. Technician A
    2. Technician B
    3. Both A and B
    4. Neither A nor B

 

  1. The states of refrigerant are being discussed. Technician A states that when a refrigerant changes from a gas to a liquid, it absorbs heat. Technician B states that when a refriger­ant changes from a liquid to a gas, it gives off heat. Who is correct?
    1. Technician A
    2. Technician B
    3. Both A and B
    4. Neither A nor B

 

  1. Air-conditioning components are being discussed. Technician A states that a restriction device can be a fixed orifice or a thermal expansion valve. Technician B states that the purpose of the compressor is to circulate refrigerant, and with the help of a restriction, control the refrigerant pressure. Who is correct?
    1. Technician A
    2. Technician B
    3. Both A and B
    4. Neither A nor B

 

  1. Refrigerant types are being discussed. Technician A states that R-134a is being phased out because it was recently found to be a major contributor to greenhouse gases. Technician B states that HFO-1234yf is non-flammable. Who is correct?
    1. Technician A
    2. Technician B
    3. Both A and B
    4. Neither A nor B

 

  1. An HVAC system is being discussed. Technician A states that on most vehicles, the MAX cold setting will pull air from the outside to provide maximum cooling. Technician B states that on some vehicles, a heater control valve blocks coolant from entering the heater core unless the heater is turned on. Who is correct?
    1. Technician A
    2. Technician B
    3. Both A and B
    4. Neither A nor B

 

  1. An HVAC system is being discussed. Technician A states that on some vehicles, the AC may be turned on automatically when defrosting the windshield since it dries the air. Technician B states that many vehicles use a blower mo­tor resistor pack to control blower motor speeds. Who is correct?
    1. Technician A
    2. Technician B
    3. Both A and B
    4. Neither A nor B

 

  1. An HVAC system is being discussed. Technician A states that water dripping from the center of the vehicle on a humid day with the AC on may be normal. Technician B states that some manufacturers are using charcoal cabin filters which trap odors and airborne pollutants before they enter the cabin. 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).

]]> Mon, 22 Sep 2025 06:42:51 PDT <![CDATA[Due: 08/16/2025]]> //www.kingsvilleisd.com/homeworkItem10641057 //www.kingsvilleisd.com/apps/classes/1061077/assignments/ 1.https://mycareertech.com/v/z2yvpx/shop-and-personal-safety
2.https://mycareertech.com/t/z2yvpx/shop-and-personal-safety
please watch the safety video and then do the test, you must score a 100, no if no and and no buts, keep taking the test 

]]> Tue, 12 Aug 2025 15:35:16 PDT