ASE A7 Heating and Air Conditioning Study Questions Part 1 - With Explanations!

WiseAutoTools presents Part One of our ASE study guide for Heating and Air Conditioning. I passed my first ASE test back in the early 1980s, ultimately becoming an ASE Master Tech. One thing that always frustrated me about the study guides I used was that they never explained the reasoning for the "wrong" answers. To truly learn, I believe it's helpful to know why a particular answer is wrong as well as the correct answer. The correct answers and explanations start in the bottom half of this page. Here's a 25-question free sample test. Read on!

1. The customer states that the A\C works for about 45 minutes before stopping. Which is most likely responsible for the problem? 

a) Expansion valve stuck closed

b) Weak Compressor Coil

c) Condenser Fan Motor

d) Evaporator Leak

2. What is the purpose of the orifice tube in an automotive A/C system? 

a) To regulate the flow of refrigerant 

b) To filter out metal debris from the refrigerant 

c) To reduce the pressure of the refrigerant 

d) To tunnel the air into the passenger compartment

3. What is the most common refrigerant used in automotive A/C systems? 

a) R-12 

b) R-22 

c) R-134a 

d) FREON

4. Which of the following is a symptom of a faulty A/C compressor? 

a) Reduced airflow through the vents 

b) Unusual smells coming from the A/C

c) Low refrigerant pressure 

d) 95PSI reading on high and low gauges

5. What is the main function of the A/C evaporator? 

a) To remove moisture from refrigerant

b) To transfer heat from the refrigerant to the outside air 

c) To regulate the flow of refrigerant 

d) To maintain cabin temperature

6. What is the role of the A/C accumulator/drier? 

a) To store excess refrigerant 

b) To remove moisture and debris from the refrigerant 

c) To regulate the flow of refrigerant 

d) To compress the refrigerant

7. Which type of refrigerant is considered more environmentally friendly? 

a) R-12 

b) R-36

c) R-134a 

d) R1234ynf

8. What is the purpose of the A/C high-pressure switch? 

a) To turn off the A/C system if the refrigerant pressure is too low 

b) To turn off the A/C system if the refrigerant pressure is too high 

c) To regulate the flow of refrigerant 

d) To ensure the desired high side pressure is obtained

9. Which of the following is a common source of A/C refrigerant leaks? 

a) Evaporator

b) Compressor

c) High Pressure Discharge Hose

d) All of the above

10. What is the role of the A/C pressure transducer? 

a) To monitor the pressure of the refrigerant in the system 

b) To regulate the flow of refrigerant 

c) To compress the refrigerant 

d) None of the above

11. Which component is responsible for removing air and moisture from the A/C system? 

a) Dessert Dry Salt Bag

b) Blower Fan

c) High Side Auxiliary Filter

d) Accumulator/drier

12. What is the function of the A/C clutch? 

a) To engage and disengage the compressor as needed 

b) To regulate the flow of refrigerant 

c) To put the compressor in gear 

d) None of the above

13. Which type of A/C system is most commonly found in most vehicles? 

a) Evaporative

b) Component system

c) Hydraulic

d) Electric driven

14. What is the role of the A/C blend door actuator? 

a) To control the flow of air through the A/C system 

b) To regulate the temperature of the air that flows through the A/C system 

c) To blend inside and outside air 

d) None of the above

15. Which of the following is a symptom of a clogged A/C condenser? 

a) Reduced airflow fin the passenger compartment

b) Dirty cabin air filter

c) High pressure switch disengaging the compressor 

d) None of the above

16. What is the function of the A/C low-pressure switch? 

a) To turn off the A/C system if the refrigerant pressure is too low 

b) To turn off the A/C system if the refrigerant pressure is too high 

c) To regulate the flow of refrigerant 

d) To cycle the compressor on and off

17. Which component is responsible for regulating the amount of refrigerant that flows through the A/C system? 

a) Accumulator/drier 

b) Expansion valve 

c) Steinberg's volumetric needle

d) Compressor

18. What is the purpose of the A/C receiver/drier? 

a) To store excess refrigerant 

b) To remove moisture and debris from the refrigerant 

c) To reduce humidity in the passenger compartment

d) To add oil to the refrigerant

19. Which component is responsible for transferring heat from the refrigerant to the air in the A/C system? 

a) Compressor 

b) Condenser 

c) Expansion valve 

d) Evaporator

20. Which of the following is a symptom of a faulty A/C expansion valve? 

a) Lack of airflow from the vents 

b) Low side line freezing up

c) AC is only cold at highway speeds

d) None of the above

21. What is the purpose of the A/C pressure relief valve? 

a) To regulate the flow of refrigerant 

b) To prevent the A/C system from over-pressurizing 

c) To alert the technician if he overcharges the system 

d) None of the above

22. Which type of A/C system requires a different type of compressor oil than traditional A/C systems? 

a) R-12 

b) R-22 

c) R-134a 

d) R-1234yf

23. What is the function of the A/C heater control valve? 

a) To prevent the AC lines from freezing up 

b) To regulate the temperature of the air that flows through the A/C system 

c) To monitor the pressure of the refrigerant in the system 

d) None of the above.

24. Which one of the following is a symptom of a problem with A/C evaporator? 

a) A sweet/sour smell in the cabin

b) Strange noises coming from the evaporator 

c) Low refrigerant pressure 

d) None of the above

25. Which component is responsible for regulating the speed of the A/C blower motor? 

a) Blower resistor 

b) A/C compressor 

c) A/C condenser 

d) A/C expansion valve

Bonus Questions - 

BQ1. Which tool should an automotive tech have when diagnosing and A/C system?

a) Manifold AC Gauge Set

b) Thermometer for checking vent air temperature

c) A/C RRR (Recovery, Recycle, Recharge) Machine

d) All of the above 

BQ2. Which of the following is a symptom of a clogged A/C expansion valve?

a) Compressor clutch slipping

b) Metal debris found in the AC lines

c) Low refrigerant pressure

d) None of the above 

BQ2. What is the role of the A/C Compressor clutch "gap"?

a) To allow the clutch to cool periodically

b) To regulate the flow of refrigerant

c) To turn off the A/C system if the refrigerant pressure is too low

d) None of the above

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Answers with explanations.

1. The customer states that the A\C works for about 45 minutes before stopping. Which is most likely responsible for the problem? 

a) Expansion valve stuck closed

b) Weak Compressor Coil

c) Condenser Fan Motor

d) Evaporator Leak

The most likely cause of the problem described by the customer is a weak compressor coil (option b). If the compressor coil is weak or operates intermittently, it may not be able to engage the clutch, resulting in the A/C compressor not pumping refrigerant through the system. The other options could also potentially cause problems with the A/C system, but they are less likely to be the root cause of the issue described by the customer.

Option a, a stuck closed expansion valve, could cause the A/C system to stop working altogether, but it would not likely cause the system to work for 45 minutes before stopping.

Option c, a faulty condenser fan motor, could cause the A/C system to stop working if there's no airflow through the condenser fins, but again, it would not likely cause the system to work for 45 minutes before stopping.

Option d, an evaporator leak, could cause a loss of refrigerant and reduced cooling capacity, but it would not likely cause the system to work for 45 minutes before stopping.

2. What is the purpose of the orifice tube in an automotive A/C system?

a) To regulate the flow of refrigerant

b) To filter out metal debris from the refrigerant

c) To reduce the pressure of the refrigerant

d) To tunnel the air into the passenger compartment 

The purpose of the orifice tube in an automotive A/C system is to regulate the flow of refrigerant (option a). The orifice tube is a small tube with a calibrated opening that creates a pressure drop in the refrigerant, which helps to regulate the flow of refrigerant through the system.

While the orifice tube can act as a filter and trap some debris, its primary function is to regulate the flow of refrigerant, not to filter out debris. The accumulator or receiver-drier is the component in the A/C system that is specifically designed to filter out debris and prevent it from circulating through the system.

Option c, to reduce the pressure of the refrigerant, is the function of the expansion valve in the A/C system. The expansion valve is designed to create a pressure drop in the refrigerant, which allows it to expand and cool as it moves through the evaporator.

Option d, to tunnel the air into the passenger compartment, is not a function of the orifice tube or any other component in the A/C system. The air is typically directed into the passenger compartment through the vents and ductwork.

3. What is the most common refrigerant used in automotive A/C systems?

a) R-12

b) R-22

c) R-134a

d) FREON 

The most common refrigerant used in automotive A/C systems today is R-134a (option c). R-12 (option a) and R-22 (option b) were previously used in automotive A/C systems, but they have been largely phased out due to their negative impact on the environment, as they are known to deplete the ozone layer.

Option d, FREON, is a bit misleading, as FREON is actually a brand name for a type of refrigerant manufactured by DuPont, which was commonly used in the past in various refrigeration systems, including automotive A/C systems. However, the use of FREON (specifically, R-12) has been banned due to its negative impact on the environment.

R-134a, on the other hand, is a more environmentally-friendly refrigerant that is widely used in modern automotive A/C systems. It has a lower ozone depletion potential and global warming potential compared to R-12 and R-22, making it a safer and more sustainable option for automotive A/C systems.

4. Which of the following is a symptom of a faulty A/C compressor? 

a) Reduced airflow through the vents

b) Unusual smells coming from the A/C system

c) Low refrigerant pressure with compressor disengaged

d) 95PSI reading on high and low gauges 

95PSI reading on high and low gauges (option d) can be a symptom of a faulty compressor. Equal refrigerant pressure readings on the high and low sides of the A/C system with the compressor engaged means the compressor is not pumping.

Option a, reduced airflow through the vents, could be caused by a variety of issues, such as a clogged cabin air filter or a malfunctioning blower motor, but it is not typically associated with a faulty compressor.

Option b, unusual smells coming from the A/C system, could be indicative of a problem with the cabin air filter or evaporator, but it is not typically associated with a faulty compressor.

Option c, low refrigerant pressure with the compressor disengaged, may be indicative of a refrigerant leak or other issue in the A/C system, but it is not necessarily a definitive symptom of a faulty compressor.

5. What is the main function of the A/C evaporator?

a) To remove moisture from refrigerant

b) To transfer heat from the refrigerant to the outside air

c) To regulate the flow of refrigerant

d) To maintain cabin temperature 

The main function of the A/C evaporator is to transfer heat from the refrigerant to the outside air (option b). The A/C evaporator is a heat exchanger that is designed to absorb heat from the air inside the vehicle and transfer it to the refrigerant. As the refrigerant absorbs heat from the evaporator, it cools the air inside the vehicle, creating a comfortable environment for the occupants.

Option a, to remove moisture from refrigerant, is the function of the accumulator or receiver-drier in the A/C system. These components contain desiccant material that absorbs moisture from the refrigerant, preventing it from circulating through the A/C system and causing damage.

Option c, to regulate the flow of refrigerant, is the function of the orifice tube or expansion valve in the A/C system. These components create a pressure drop in the refrigerant, which regulates its flow through the system.

Option d, to maintain cabin temperature, is the function of the thermostat and temperature control system in the vehicle, which regulates the operation of the A/C system to maintain the desired cabin temperature.

6. What is the role of the A/C accumulator/drier?

a) To store excess refrigerant

b) To remove moisture and debris from the refrigerant

c) To regulate the flow of refrigerant

d) To compress the refrigerant The role of the A/C accumulator/drier is to remove moisture and debris from the refrigerant (option b). The accumulator/drier is a component in the A/C system that is designed to remove any moisture that may be present in the refrigerant. Moisture in the refrigerant can cause damage to the A/C system and reduce its efficiency. In addition to removing moisture, the accumulator/drier also contains desiccant material that traps debris and other contaminants that may be present in the refrigerant.

Option a, to store excess refrigerant, is not a function of the accumulator/drier. The refrigerant is circulated through the A/C system continuously and is not stored in any one component.

Option c, to regulate the flow of refrigerant, is the function of the orifice tube or expansion valve in the A/C system. These components create a pressure drop in the refrigerant, which regulates its flow through the system.

Option d, to compress the refrigerant, is the function of the A/C compressor in the A/C system. The compressor is responsible for compressing the low-pressure refrigerant vapor and raising its temperature and pressure so that it can be circulated through the A/C system.

7. Which type of refrigerant is considered more environmentally friendly?

a) R-12

b) R-36

c) R-134a

d) R1234ynf The most environmentally friendly refrigerant among the options given is R1234ynf (option d). R-12 (option a) is not considered environmentally friendly due to its chlorine content, which has been found to contribute to the depletion of the Earth's ozone layer. R-36 (option b) is not a valid refrigerant type and does not exist. While R-134a (option c) is considered more environmentally friendly than R-12 or R-22, it still has a relatively high global warming potential (GWP), which means that it has the potential to contribute to climate change.

R1234ynf, on the other hand, has a much lower GWP than R-134a and is considered to be one of the most environmentally friendly refrigerants currently available for automotive A/C systems. R1234ynf is also a hydrofluoroolefin (HFO), which is a newer class of refrigerants that are designed to have lower environmental impact.

8. What is the purpose of the A/C high-pressure switch?

a) To turn off the A/C system if the refrigerant pressure is too low

b) To turn off the A/C system if the refrigerant pressure is too high

c) To regulate the flow of refrigerant

d) To ensure the desired high side pressure is obtained The purpose of the A/C high-pressure switch is to turn off the A/C system if the refrigerant pressure is too high (option b). The high-pressure switch is designed to protect the A/C system from damage caused by excessively high pressure, which can occur if there is a restriction in the system or if the system is overcharged with refrigerant.

Option a, to turn off the A/C system if the refrigerant pressure is too low, describes the function of the A/C low-pressure switch, which is designed to protect the A/C system from damage caused by excessively low pressure, such as may occur if there is a refrigerant leak or if the system is undercharged with refrigerant.

Option c, to regulate the flow of refrigerant, is not the primary purpose of the high-pressure switch, although it may play a secondary role in this function.

Option d, to ensure the desired high side pressure is obtained, is not the purpose of the high-pressure switch, and has no bearing on how high the pressure gets.

9. Which of the following is a common source of A/C refrigerant leaks?

a) Evaporator

b) Compressor

c) High Pressure Discharge Hose

d) All of the above

All of the above options (option d) are common sources of A/C refrigerant leaks.

The evaporator (option a) is a common source of leaks due to its location inside the passenger compartment and its exposure to moisture and debris.

The compressor (option b) is a common source of leaks due to the high pressures and temperatures involved in its operation, which can cause seals and gaskets to fail over time.

The high-pressure discharge hose (option c) is a common source of leaks due to its location in the engine compartment, where it can be exposed to heat, vibration, and other sources of mechanical stress.

10. What is the role of the A/C pressure transducer?

a) To monitor the pressure of the refrigerant in the system

b) To regulate the flow of refrigerant

c) To compress the refrigerant

d) None of the above 

The role of the A/C pressure transducer is to monitor the pressure of the refrigerant in the system (option a). The pressure transducer is a sensor that is typically located at the high-pressure side of the A/C system and is designed to measure the pressure of the refrigerant as it passes through the system. The pressure transducer sends a signal to the A/C control module or other control device, which can then use this information to regulate the operation of the compressor, expansion valve, or other components of the A/C system.

Option b, to regulate the flow of refrigerant, is the role of the expansion valve or other flow control device.

Option c, to compress the refrigerant, is the role of the A/C compressor.

Option d, none of the above, is not correct, as option a accurately describes the role of the A/C pressure transducer in the A/C system.

11. Which component is responsible for removing air and moisture from the A/C system?

a) Dessert Dry Salt Bag

b) Blower Fan

c) High Side Auxiliary Filter

d) Accumulator/drier

The component responsible for removing air and moisture from the A/C system is the accumulator/drier (option d). The accumulator/drier is typically located on the low-pressure side of the A/C system and is designed to trap and remove any moisture or debris that may be present in the refrigerant. The accumulator/drier also acts as a temporary storage container for excess refrigerant and helps to maintain a consistent flow of refrigerant through the system.

Option a, dessert dry salt bag, is not a component used in A/C systems and is not responsible for removing air or moisture from the system.

Option b, blower fan, is responsible for moving air through the A/C system and into the passenger compartment, but it does not remove air or moisture from the system.

Option c, high side auxiliary filter, is not typically used in A/C systems and is not responsible for removing air or moisture from the system.

12. What is the function of the A/C clutch?

a) To engage and disengage the compressor as needed

b) To regulate the flow of refrigerant

c) To put the compressor in gear

d) None of the above

The function of the A/C clutch is to engage and disengage the compressor as needed (option a). The A/C clutch is a component that is typically located on the front of the compressor and is responsible for engaging and disengaging the compressor shaft from the drive belt. When the A/C is turned on, the clutch is engaged, causing the compressor to start circulating refrigerant through the A/C system. When the A/C is turned off, the clutch is disengaged, stopping the flow of refrigerant through the system.

Option b, to regulate the flow of refrigerant, is the role of the expansion valve or other flow control device.

Option c, to put the compressor in gear, is not a function of the A/C clutch.

Option d, none of the above, is not correct, as option a accurately describes the function of the A/C clutch in the A/C system.

13. Which type of A/C system is most commonly found in most vehicles?

a) Evaporative

b) Component system

c) Hydraulic

d) Electric driven

The type of A/C system that is most commonly found in most vehicles is the component system (option b). Component systems are the most widely used A/C systems in automotive applications, as they are relatively simple, reliable, and efficient. Component systems typically consist of a compressor, condenser, evaporator, expansion valve or orifice tube, and various hoses and fittings, and they operate using a closed-loop refrigerant cycle to cool and dehumidify the air in the passenger compartment.

Option a, evaporative systems, are not used in automotive A/C applications, as they are primarily used to cool water in industrial or agricultural applications.

Option c, hydraulic systems, are also not used in automotive A/C applications. While hydraulic systems can be used to transfer power in a vehicle, they are not typically used to power A/C systems in passenger vehicles.

Option d, electric-driven systems, are not commonly used in automotive A/C applications, although some electric vehicles may use electric compressors or other components in the A/C system. However, component systems remain the most widely used type of A/C system in most vehicles.

14. What is the role of the A/C blend door actuator?

a) To control the flow of air through the A/C system

b) To regulate the temperature of the air that flows through the A/C system

c) To blend inside and outside air

d) None of the above 

The role of the A/C blend door actuator is to regulate the temperature of the air that flows through the A/C system (option b). The blend door actuator is typically a small motor that is located near the A/C evaporator or heater core and is responsible for moving a series of blend doors or flaps that control the flow of air through the system. By opening and closing these blend doors, the blend door actuator can control the amount of hot or cold air that is mixed together to achieve the desired temperature in the passenger compartment.

Option a, to control the flow of air through the A/C system, is the role of the A/C mode door actuator, which controls the direction of the airflow through the A/C system.

Option c, to blend inside and outside air, is the role of the A/C recirculation door or fresh air door, which controls whether outside air or recirculated air is used for ventilation.

Option d, none of the above, is not correct, as option b accurately describes the role of the A/C blend door actuator in the A/C system.

15. Which of the following is a symptom of a clogged A/C condenser?

a) Reduced airflow fin the passenger compartment

b) Dirty cabin air filter

c) High pressure switch disengaging the compressor

d) None of the above 

High pressure switch disengaging the compressor, is a potential symptom of a clogged A/C condenser (option c). A clogged A/C condenser can cause high pressure in the A/C system, which can cause the high-pressure switch to disengage the compressor.

Option a, reduced airflow in the passenger compartment, is not typically associated with a clogged A/C condenser, as the condenser is located in front of the radiator and does not directly affect airflow through the cabin.

Option b, a dirty cabin air filter, can affect the efficiency of the A/C system but is not specifically related to a clogged condenser.

Option d, none of the above, is not correct, as option c accurately describes a potential symptom of a clogged A/C condenser.

16. What is the function of the A/C low-pressure switch?

a) To turn off the A/C system if the refrigerant pressure is too low

b) To turn off the A/C system if the refrigerant pressure is too high

c) To regulate the flow of refrigerant

d) To cycle the compressor on and off

The function of the A/C low-pressure switch is to turn off the A/C system if the refrigerant pressure is too low (option a). The low-pressure switch is typically located on the suction side of the A/C system, downstream of the evaporator. It is designed to protect the compressor from damage by shutting off the A/C system if the refrigerant charge is too low, which can cause the compressor to run dry and overheat.

Option b, to turn off the A/C system if the refrigerant pressure is too high, is the function of the A/C high-pressure switch.

Option c, to regulate the flow of refrigerant, is the function of the expansion valve or orifice tube.

Option d, to cycle the compressor on and off, is the function of the A/C clutch cycling switch or pressure cycling switch.

17. Which component is responsible for regulating the amount of refrigerant that flows through the A/C system?

a) Accumulator/drier

b) Expansion valve

c) Steinberg's volumetric needle

d) Compressor 

The component responsible for regulating the amount of refrigerant that flows through the A/C system is the expansion valve (option b). The expansion valve is located at the evaporator inlet and is designed to regulate the flow of refrigerant into the evaporator, based on the temperature and pressure of the refrigerant leaving the evaporator.

Option a, the accumulator/drier, is responsible for removing moisture and debris from the refrigerant and storing excess refrigerant.

Option c, Steinberg's volumetric needle, is not a component used in automotive A/C systems.

Option d, the compressor, is responsible for circulating the refrigerant through the A/C system, but it does not regulate the amount of refrigerant that flows through the system.

18. What is the purpose of the A/C receiver/drier?

a) To store excess refrigerant

b) To remove moisture and debris from the refrigerant

c) To reduce humidity in the passenger compartment

d) To add oil to the refrigerant

The purpose of the A/C receiver/drier is to remove moisture and debris from the refrigerant (option b). The receiver/drier is typically located on the high-pressure side of the A/C system, downstream of the condenser. It contains a desiccant material that absorbs moisture and traps debris, preventing them from circulating through the A/C system and causing damage to the compressor or other components.

Option a, to store excess refrigerant, is the function of the accumulator/drier.

Option c, to reduce humidity in the passenger compartment, is the function of the evaporator.

Option d, to add oil to the refrigerant, is not the function of the A/C receiver/drier. However, oil is often added to the refrigerant during A/C service to ensure that the compressor and other components are properly lubricated.

19. Which component is responsible for transferring heat from the refrigerant to the air in the A/C system?

a) Compressor

b) Condenser

c) Expansion valve

d) Evaporator 

The component responsible for transferring heat from the refrigerant to the air in the A/C system is the condenser (option b). The condenser is typically located at the front of the vehicle, in front of the radiator. It is designed to dissipate the heat absorbed by the refrigerant in the evaporator and release it into the outside air.

Option a, the compressor, is responsible for circulating the refrigerant through the A/C system.

Option c, the expansion valve, is responsible for regulating the flow of refrigerant into the evaporator.

Option d, the evaporator, is responsible for absorbing heat from the air in the passenger compartment, cooling and dehumidifying the air.

20. Which of the following is a symptom of a faulty A/C expansion valve?

a) Lack of airflow from the vents

b) Low side line freezing up

c) AC is only cold at highway speeds

d) None of the above

The symptom of a faulty A/C expansion valve is a low side line freezing up (option b). If the expansion valve is not functioning properly, it can cause a restriction in the refrigerant flow, resulting in low pressure and temperature readings on the low side of the A/C system. This can cause the moisture in the refrigerant to freeze and accumulate on the low side lines.

Option a, lack of airflow from the vents, is typically associated with a problem in the blower motor or a clogged cabin air filter.

Option c, the A/C only being cold at highway speeds, is typically associated with a problem in the condenser or a malfunctioning cooling fan.

21. What is the purpose of the A/C pressure relief valve?

a) To regulate the flow of refrigerant

b) To prevent the A/C system from over-pressurizing

c) To alert the technician if he overcharges the system

d) None of the above

The purpose of the A/C pressure relief valve is to prevent the A/C system from over-pressurizing (option b). The pressure relief valve is typically located on the high-pressure side of the A/C system, downstream of the compressor. If the pressure in the A/C system exceeds a certain threshold, the relief valve will open, releasing refrigerant and reducing the pressure in the system. This prevents damage to the A/C system components and potential safety hazards.

Option a, to regulate the flow of refrigerant, is the function of the expansion valve or orifice tube.

Option c, to alert the technician if he overcharges the system, is not the function of the A/C pressure relief valve. However, some A/C systems may have a pressure switch that alerts the technician if the system is overcharged.

Option d, none of the above, is not correct, as option b is the correct answer.

22. Which type of A/C system requires a different type of compressor oil than traditional A/C systems?

a) R-12

b) R-22

c) R-134a

d) R-1234yf 

The type of A/C system that requires a different type of compressor oil than traditional A/C systems is R-1234yf (option d). R-1234yf is a newer refrigerant that has been introduced as a more environmentally friendly alternative to R-134a. However, R-1234yf is not compatible with the mineral or synthetic compressor oils commonly used in traditional A/C systems. Instead, specialized polyalkylene glycol (PAG) oils are required for use with R-1234yf.

Options a, b, and c are not correct, as they do not require a different type of compressor oil than traditional A/C systems. Always make sure the oil you are adding is for the type of system being serviced.

23. What is the function of the A/C heater control valve?

a) To prevent the AC lines from freezing up

b) To regulate the temperature of the air that flows through the A/C system

c) To monitor the pressure of the refrigerant in the system

d) None of the above. The function of the A/C heater control valve is to regulate the flow of hot engine coolant into the heater core, which in turn controls the temperature of the air that flows through the A/C system (option b). The A/C heater control valve is typically operated by a cable or electronic actuator that opens and closes the valve to allow hot coolant to flow through the heater core and warm up the air that flows through the A/C system.

Option a is not correct, as preventing AC lines from freezing up is typically accomplished through the use of an orifice tube or expansion valve that regulates the flow of refrigerant through the system. Option c is also not correct, as monitoring the pressure of the refrigerant in the system is typically the role of pressure sensors and switches, not the A/C heater control valve. Option d is not correct, as the A/C heater control valve serves a specific function in controlling the temperature of the air that flows through the A/C system.

24. Which one of the following is a symptom of a problem with A/C evaporator?

a) A sweet/sour smell in the cabin

b) Strange noises coming from the evaporator

c) Low refrigerant pressure

d) None of the above

One of the symptoms of a faulty A/C evaporator can be a sweet/sour smell in the cabin (option a). This smell is typically caused by the buildup of bacteria and mold on the evaporator's surface, which can occur due to moisture condensation on the evaporator coil. The moisture provides a favorable environment for the growth of bacteria and mold, which can cause the odor to emanate from the A/C system. It's also important to note that a heater core leak may also have a sweet/sour smell due to coolant leaking inside the passenger compartment and/or HVAC system.

Option b, strange noises coming from the evaporator, could be an indication of a problem with the blower motor or other components of the A/C system, but it is not necessarily a definitive symptom of a faulty evaporator.

Option c, low refrigerant pressure, could be an indication of a problem with the compressor, expansion valve, or other components of the A/C system, but it is not necessarily a definitive symptom of a faulty evaporator.

25. Which component is responsible for regulating the speed of the A/C blower motor?

a) Blower resistor

b) A/C compressor

c) A/C condenser

d) A/C expansion valve

The component that is responsible for regulating the speed of the A/C blower motor is the blower resistor (option a). The blower resistor is a small electrical component located near the blower motor that controls the voltage and amperage sent to the blower motor. By doing so, it can control the speed of the blower motor and the amount of air flowing through the A/C system.

Option b, A/C compressor, is responsible for compressing and circulating the refrigerant through the A/C system. It is not directly involved in regulating the speed of the blower motor.

Option c, A/C condenser, is responsible for removing heat from the refrigerant as it flows through the A/C system. It is not directly involved in regulating the speed of the blower motor.

Option d, A/C expansion valve, is responsible for regulating the flow of refrigerant through the A/C system. It is not directly involved in regulating the speed of the blower motor.

Bonus Questions

BQ1. Which tool should an automotive tech have when diagnosing and A/C system?

a) Manifold AC Gauge Set

b) Thermometer for checking vent air temperature

c) A/C RRR (Recovery, Recycle, Recharge) Machine

d) All of the above

The correct answer is d) An automotive technician should have all of the following tools when diagnosing an A/C system: a) Manifold AC Gauge Set for measuring high and low side pressures in the A/C system. b) Thermometer for checking vent air temperature to ensure proper cooling performance. c) A/C RRR (Recovery, Recycle, Recharge) Machine for evacuating and recharging the A/C system with refrigerant. Therefore, the correct answer is d) All of the above.

BQ2. Which of the following is a symptom of a clogged A/C expansion valve?

a) Compressor clutch slipping

b) Metal debris found in the AC lines

c) Low refrigerant pressure

d) None of the above 

The correct answer is option c) Low refrigerant pressure. A clogged A/C expansion valve can restrict the flow of refrigerant through the system, leading to a decrease in pressure downstream of the valve. This can result in low refrigerant pressure readings, which can cause reduced cooling performance and other issues with the A/C system.

Option a) Compressor clutch slipping could be a symptom of a faulty clutch or other issues with the compressor, but it is not necessarily indicative of a clogged expansion valve.

Option b) Metal debris found in the A/C lines could be a sign of a compressor or other component failure, but it is not typically associated with a clogged expansion valve.

Option d) None of the above is not correct as a clogged expansion valve can lead to low refrigerant pressure and other related issues.

BQ2. What is the role of the A/C Compressor clutch "gap"?

a) To allow the clutch to cool periodically

b) To regulate the flow of refrigerant

c) To turn off the A/C system if the refrigerant pressure is too low

d) None of the above

The role of the A/C Compressor clutch "gap" is to allow the clutch to disengage (option a). The clutch gap is a small distance between the clutch plate and pulley, which allows the clutch to disengage when the A/C system is turned off. This prevents the compressor from continuously turning and using energy when it is not needed, and also reduces wear on the clutch components. When the A/C system is turned on, the magnetic field produced by the clutch coil pulls the clutch plate towards the pulley, closing the gap and engaging the compressor.

Option b, to regulate the flow of refrigerant, is not the role of the A/C Compressor clutch gap.

Option c, to turn off the A/C system if the refrigerant pressure is too low, is the role of the A/C low-pressure switch, not the Compressor clutch gap.

Option d, none of the above, is incorrect as option a is the correct answer.