ASE A7 Heating and Air Conditioning Q & A Part 3

ASE Practice Test Questions & Answers with Explanation

1. All of the following are true statements concerning in-line filters EXCEPT:
A. They are usually installed in a system that has suffered a compressor failure.
B. They are installed to protect the new compressor from metal chips or other debris that could be in the system from the original compressor failure.
C. They are installed to collect debris that could clog the orifice tube or expansion valve filters.
D. Filters are only installed in the high side of the system.
The correct answer is D There are filters that fit into both the high and low sides of the system. All of the other statements ate true concerning in-line filters.

2. A customer with an ATC (automatic temperature control) equipped vehicle complains that the car does not get cool enough on hot days. Technician A says that the programmer is the problem. Technician B says that the blend door actuator could be the problem. Who is correct?
A. Technician A only
B. Technician B only
C. Both A and B
D. Neither A or B
The correct answer is D Both technicians are incorrect. To a find the problem you cannot jump to conclusions before performing a logical diagnostic procedure or parts may be replaced unnecessarily. This includes performing a preliminary inspection of the A/C system and checking refrigerant pressures before condemning any part of the ATC system.

3. A customer complains that when accelerating his car with the A/C on, the cold air flow from the dash
outlets shifts to the floor. Technician A says that this is caused by a faulty check valve in the vacuum
reservoir. Technician B says that this condition is due to a vacuum leak. Who is right?
A. Technician A only
B. Technician B only
C. Both A and B
D. Neither A or B
The correct answer is C If, during hard acceleration, air routing changes by itself, it’s probably due to a leak in the system or a faulty check valve in the vacuum reservoir. A complaint that the mode shifts from the dash to the floor at wide-open throttle is evidence that the system isn’t holding vacuum.

4. Technician A says “U” DTCs indicate there is nothing wrong with the A/C system. Technician B say when there is a “U” DTC, it should be repaired before any further diagnostics can be performed. Who is correct?
A. Technician A only
B. Technician B only
C. Both Technician A and B
D. Neither Technician A or B
The correct answer is B A “U” DTC indicates there is a problem with the present modules not being able to communicate with each other. It is likely that the module responsible for generating a DTC for the A/C problem can’t report the problem until it is able to communicate on the network. Repair the “U” DTC first then rescan for any present DTCs.

5. The compressor in an A/C system does not run. When a jumper wire is used to connect the battery positive terminal to the power connector, the compressor clutch engages. Technician A says that the clutch coil is defective. Technician B says that the pressure cycling switch could be defective. Who is correct?
A. Technician A only
B. Technician B only
C. Both A and B
D. Neither A or B
The correct answer is B Technician A is wrong because if the clutch coil was defective, the compressor clutch would not engage. Technician B is correct because, since the compressor clutch engages when 12 volts is directly applied, the problem is in the compressor control circuit, which includes the pressure cycling switch.

6. Which of the following sensors is NOT an NTC thermistor?
A. Sunload sensor
B. Ambient sensor
C. In-vehicle sensor
D. ECT (engine coolant temperature) sensor
The correct answer is A The sunload sensor is a photovoltaic diode. All of the other sensors listed are NTC thermistors.

7. Observing the data stream while operating a HVAC system on a late model vehicle with Automatic Temperature Control (ATC) the counts for the blend door change when the vehicle is moved outside in the mid day sun. Technician A says that under no circumstances should the counts change on the blend door motor. Technician B says there is an intermittent problem with the blend door actuator that will eventually set a DTC. Who is correct?
A. Technician A only
B. Technician B only
C. Both A and B
D. Neither A or B
The correct answer is D This is it’s normal operation.The blend door motor counts change as the position of the door is changed. The easiest was to determine the blend door is functions is to read the data stream from the scan tool while observing the system’s operation.

8. Technician A says that an ambient temperature sensor provides input for the ATC (Automatic Temperature Control) system. Technician B says that an ambient temperature switch protects the compressor from damage. Who is correct?
A. Technician A only
B. Technician B only
C. Both A and B
D. Neither A or B
The correct answer is C In non-ATC systems, the function of the ambient temperature switch is to inhibit compressor dutch operation in cold ambient temperatures. This function mainly protects the compressor from poor or no lubrication, which could be the result of cold refrigerant oil. In ATC systems, the ambient temperature sensor senses ambient outside temperature. As ambient or interior temperatures stray, the sensors pick up the change and the system adjusts the outlet duct temperature accordingly to compensate for the temperature changes.

9. The floor inside a vehicle is wet and there is a slimy film on the windows. Technician A says that the heater core is leaking. Technician B says that the evaporator case drain plug is clogged. Who is correct?
A. Technician A only
B. Technician B only
C. Both A and B
D. Neither A or B
The correct answer is A Fogged windows that smear when wiped and moisture on the passenger floor are telltale signs of a leaking heater core. Technician B is incorrect because, while a clogged evaporator case drain could cause the case to fill up with:moisture and spill out onto the floor, it would not cause a slimy film on the windows.

10. When diagnosing an ATC (Automatic Temperature Control) system, most of the system temperature sensors can be tested for:
A. Resistance and current flow
B. Resistance and voltage drop
C. Voltage drop and current flow
D. Current flow and continuity
The correct answer is B Most temperature sensors can be tested for resistance and voltage drop. In general, the sensor should be replaced if its resistance is not within specification. Since a temperature sensor’s resistance varies with temperature, check the sensor voltage against temperature and compare to manufacturer’s specifications.

11. The A/C compressor cycles rapidly, and air coming from the vents is only slightly cool. Technician
A says the problem could be a low refrigerant charge. Technician B says the problem could be a defective thermostatic switch. Who is correct?
A. Technician A only
B. Technician B only
C. Both A and B
D. Neither A or B
The correct answer is C During operation, the clutch may cycle on and off several times each minute. Insufficient refrigerant causes rapid change in heat load on the evaporator, which affects system pressures. If the clutch cycles rapidly, it may be a sign of low refrigerant charge. A defective thermostatic switch may not be engaging the compressor clutch long enough. The thermostatic switch has a capillary tube attached to the evaporator outlet or inserted between the evaporator core fins to sense the temperature. This capillary is attached to a switch that opens and closes, as necessary, to cycle the compressor.

12. Technician A says that a special tool is required to disconnect and connect spring lock fittings.
Technician B says that new when assembling spring lock fittings, new 0-rings lubricated with clean
refrigerant oil should be used. Who is correct?
A. Technician A only
B. Technician B only
C. Both A and B
D. Neither A or B
The correct answer is B Technician A is wrong because a special tool is only required to disconnect spring lock fittings.

13. When an A/C system is operating, a clicking or buzzing noise is heard coming from the compressor. Technician A says that this noise means that the system is overcharged. Technician B says that the noise could be due to air in the system. Who is correct?
A. Technician A only
B. Technician B only
C. Both A and B
D. Neither A or B
The correct answer is C A clicking or buzzing noise coming from the compressor is a sign that the system is overcharged and liquid refrigerant is entering the compressor. Unless some refrigerant is removed, severe compressor damage may result. This noise could also result from air in the system.

14. All of the following are true statements about receiver/driers EXCEPT:
A. They may have a sight glass located on the top.
B. They store liquid refrigerant.
C. They keep liquid refrigerant from entering the compressor.
D. They contain a desiccant to absorb moisture from the system.
The correct answer is C The receiver/drier is located in the high side of the system, between the condenser and evaporator, ahead of the expansion valve. It stores liquid refrigerant until needed by the evaporator. The accumulator is the component that keeps liquid refrigerant from entering the compressor, but accumulators are used in systems with orifice tubes, not expansion valves.

15. Technician A says that the A/C system can be charged through the high or low side only when the
engine is not running. Technician B says .that the A/C system can be charged though the low slde when the engine is running. Who is correct?
A. Technician A only
B. Technician B only
C. Both A and B
D. Neither A or B
The correct answer is C Charging the system can be performed through either the high side or low side when the engine is not running, but must be done only through the low side when the engine is running. This safety measure prevents high-side pressure from entering the refrigerant container and possibly causing an explosion.

16. All of the following are causes for fan clutch replacement EXCEPT:
A. Oil film on the back of the clutch
B. When the engine is hot, fan stops spinning in only two seconds after shut down
C. Fan speed does not increase as engine warms up
D. No viscous drag
The correct answer is B A properly operating clutch should stop the fan from spinning within two seconds after a hot engine shut down. All of the other answers are indications of a defective fan dutch.

17. If a capillary tube were to break at some point between its sensing bulb and the expansion valve, what affect would it have on the valve?
A. The expansion valve would stick open.
B. The expansion valve would stick closed.
C. The expansion valve would stick in whatever position it was in at the time of the break.
D. There would be no affect on the expansion valve.
The correct answer is B Expansion valves are usually spring loaded devices with a diaphragm that is linked to a plunger. Without any pressure against the diaphragm from the gas in the capillary tube, the spring inside the expansion valve would cause the valve to stick closed.

18. A major cause for the depletion of the ozone layer has been attributed to:
A. CO (carbon monoxide) fumes from automotive exhaust
B. Unburned HC (hydrocarbon) emissions from automobile exhaust
C. The release of CFCs (chlorofluorocarbons) into the atmosphere
D. All of the above
The correct answer is C The release of CFCs into the atmosphere has been found to be a major cause of ozone layer depletion.

19. A compressor clutch will not engage. All of the following could be the cause EXCEPT:
A. An open ambient temperature switch
B. Low refrigerant level
C. A closed high-pressure cutout switch
D. Faulty compressor clutch coil
The correct answer is C All of the other answers would cause the compressor clutch not to engage. The high-pressure cutout switch is normally closed. It opens the compressor clutch circuit when high-side pressures are excessive in order to protect the compressor. After an inspection of the A/C system including all of the sensors. Everything checks ok

20. The cooling fan works on high speed but not on low speed. All of the following are possible causes EXCEPT:
A. A poor connection at the junction of circuit 13S and the power distribution box
B. An open in circuit 30S
C. A faulty fan control resistor
D. An open in circuit 15 between the 15/15S splice and the fan motor.
The correct answer is D If there is an open in circuit 15 between the 15/155 splice and the fan motor, the motor will not run at all. All of the other answers are possible causes for no low speed blower motor operation.

21. The ambient temperature sensor in an ATC (automatic temperature control) system is being tested. Technician A says that, as the sensor resistance changes, the computer reads the change in voltage drop across the sensor. Technician B says that the resistance of the sensor should increase as it is heated. Who is correct?
A. Technician A only
B. Technician B only
C. Both A and B
D. Neither A or B
The correct answer is A Technician B is incorrect because the ambient temperature sensor is an NTC (Negative Temperature Coefficient) thermistor. When an NTC thermistor is heated, the resistance should drop, and when it is cooled, resistance should increase.

22. An A/C system retrofit is being discussed by two Technicians. Technician A says that the receiver/drier should be replaced. Technician B says that a high-pressure cutout switch must be added to the system. Who is correct?
A. Technician A only
B. Technician B only
C. Both A and B
D. Neither A or B
The correct answer is C The receiver/drier should be replaced because all refrigerants do not use the same type of desiccant. Rl34a systems use XH-7 or XH-9 desiccant. A high-pressure cutout switch must be added to the system to stop compressor operation before highside pressure reaches the point of opening the highpressure relief valve and releasing refrigerant into the atmosphere. This only needs to be done if it does not already have one.

23. Technician A says that mineral deposits can restrict air flow through the radiator. Technician B says that internal restrictions in the radiator can be detected from the outside. Who is correct?
A. Technician A only
B. Technician B only
C. Both A and B
D. Neither A or B
The correct answer is B Technician A is wrong because mineral deposits can restrict coolant flow inside the radiator, not air flow through the radiator. Look inside the radiator for large amounts of mineral deposits at the ends of the core tubes. Technician B is right because an infrared surface thermometer can be used to scan the surface of the radiator. With the engine hot and idling, the radiator should be warmest near the inlet and gradually cool toward the outlet. If there are areas that are considerably cooler than the inlet, then there may be restrictions at those areas.

24. The blower motor works on all speeds except low. Technician A says that this could be caused by an open in circuit 14S between the P/BL and P/0 splice and the motor. Technician B says that this could be caused by an open in the 1.8-ohm resistor. Who is correct?
A. Technician A only
B. Technician B only
C. Both A and B
D. Neither A or B
The correct answer is B If there is an open between the P/BL and P/O splice and the motor, the motor will not run at all, therefore Technician B is incorrect.

25. During replacement of a blend door actuator, Technician A says that after replacing the actuator, one procedure for recalibrating the control module would be to remove the fuse for the module for at least 60 seconds, then replace the fuse and perform an operational test of the system. Technician B says that after installing the actuator, the control module will automatically know what the step the actuator is on and there is no need for calibration. Who is correct?
A. Technician A only
B. Technician B only
C. Both Technician A and B
D. Neither Technician A or B.
The correct answer is A On some Automatic A/C systems the Body Control Module or HVAC module will automatically control the actuator and position it within limits for normal operation when the module is reset by removing its power for more than 60 seconds.

This post was written by: Martin Hand

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Martin Hand

About Martin Hand

ASE Certified L1 Advanced Mastertech. Martin Hand has over 15 years experience in Asian and European Import Auto Repair. Specializing in electrical diagnosis, engine performance, AT/MT transmission repair/rebuild. Martin is also pursuing a degree in Computers Science & Information Systems starting at Portland Community College while he plans to transfer to OIT. Certified in Java application level programming, experienced with other languages such as PHP, Ruby, JavaScript and Swift. Martin has future plans of automotive diagnostic software development.