ASE A7 Heating and Air Conditioning Q & A Part 2

ASE Practice Test Questions & Answers with Explanation

1. A vacuum door actuator is being tested. When vacuum is applied with a hand held vacuum pump, the door does not move and the reading on the vacuum gauge is zero. Technician A says that the door does not move because it is binding or obstructed. Technician B says that the door does not move because the actuator is 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 Regardless of what condition the door is in, the key here is that the gauge·reading is zero, meaning there is a vacuum leak in the actuator.

2. When the A/C damper door switch is placed in the MAX A/C position, the compressor clutch does not engage. However, a test light illuminates when placed at pin 1 of the A/C damper door switch. Which of the following could be the cause?
A. An open in the P/BL wire of circuit 14S
B. Faulty A/C damper door switch
C. Blown 30 amp fuse
D. Faulty A/C heater blower relay
The correct answer is B Since the test light showed that there is power going to the A/C damper door switch, all of the other components listed are OK. A faulty A/C damper door switch or a problem in the circuit between the switch and the A/C clutch cycling switch could be the problem.

3. The readings shown above are taken with the A/C system operating at an ambient (outside) temperature of 85°F. What do the readings indicate?
A. Normal operation
B. Low refrigerant level
C. A restriction in the high side
D. Damaged compressor
The correct answer is B Low pressure on both the low side and the high side indicates a low refrigerant charge.

4. A vehicle’s air conditioner blows cold air at normal speeds, but warm air while sitting at stop lights. The least-likely cause of this conditon is:
A. an overheating engine.
B. a weak electric fan motor.
C. a frozen expansion valve.
D. debris in the condenser fins.
The correct answer is C Excessive engine heat affects the ability of the condenser to transfer heat, therefore answer A is incorrect. While the vehicle is moving, ram air is passing through the condenser. While at a stop, the weak fan motor is not pulling enough air through, resulting in a loss of heat transfer, therefore answer B is incorrect. This is a least likely type question. Once the expansion valve freezes, the A/C would have poor performance at all speeds, therefore answer C is correct. Debris on the condenser fins reduces the ability of the condenser to transfer heat. This is even more pronounced when the vehicle is at rest, therefore answer D is incorrect.

5. All of the following are classifications of antifreeze EXCEPT:
A. IAT (Inorganic Additive Technology)
B. OAT (Organic Additive Technology)
C. HIAT (Hybrid Inorganic Additive Technology)
D. HOAT (Hybrid Organic Additive Technology)
The correct answer is C Inorganic Additive Technology (IAT) antifreeze uses inorganic phosphates and silicates to provide corrosion protection. Organic Additive Technology (OAT) antifreeze uses organic acids to protect then iron and aluminum in the cooling system. Hybrid Organic Additive Technology (HOAT) antifreeze uses both silicate and organic acid corrosion inhibitors for extended service life.

6. When recovering refrigerant from an A/C system, how long should the technician wait after the recovery/recycling unit has been turned off to see if there is any residual pressure in the system?
A. 1 minute
B. 5 minutes
C. 10 minutes
D. 15 minutes
The correct answer is B The technician should wait five minutes and watch the gauges to see if there is any residual pressure. If there is, repeat the process to remove any remaining refrigerant until the A/C system holds a stable vacuum for at least five minutes.

7. Two technicians are discussing sight glass observations. Technician A says that if foam is seen in the sight glass, the refrigerant charge is low. Technician B says that if oil streaks are seen in the sight glass, the refrigerant charge is low. 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 If there is foam, the charge is low, but if there are only a couple of bubbles, it is probably OK. A few bubbles when the compressor cycles on is normal. Oil streaks in the sight glass usually indicate a low charge and that the compressor is pumping oil from its sump.

8. A compressor clutch coil is being tested. There are 12 volts at the connector and the ground is good. The resistance of the coil is 0.00 Ohms. Technician A says the coil has an open in it’s windings. Technician B says the clutch coil has a short and has failed the resistance test. Who is correct?
A. Technician A
B. Technician B
C. Both Technicians A and B
D. Neither Technician A or B
The correct answer is B A reading of 0.00 Ohms indicates that there’s a short in the coil windings. A reading of infinity indicates there is an open in the windings. Typically the resistance of an A/C clutch coil is 2 – 5 Ohms, therefore Technician A is incorrect. The test indicates that the circuit is providing within a volt of battery/charging voltage which is good, but indicates that there’s a short in the coil. The clutch coil must be replaced, therefore Technician B is correct.

9. A customer complains that when when attempting to parallel park his vehicle it stalls repeatedly only when the air conditioning is on. Technician A says that the power steering pressure switch is defective. Technician B says that there is a problem with the power steering pump. 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 The power steering pressure switch is installed in the power steering system and reports on high pressure conditions caused by a load being placed on the engine by the power steering pump. The computer may decide to temporarily shut down the compressor to prevent engine stalling or low idle speed, or it could also raise idle speed through control of an idle speed control device. During parallel parking maneuvers, the steering wheel is most likely being moved to full lock at some point, increasing pressure. Technician A is right because, if this increased pressure is not being communicated to the computer by the switch, the A/C compressor will continue to run with its load on the engine or the idle speed will not be raised enough to keep the engine from stalling. Technician B is wrong because if the problem was with the power steering pump, the stalling would occur regardless of whether the A/C was on.

10. What is the minimum system pressure necessary to leak test with an electronic leak detector?
A. 25 psi
B. 50 psi
C. 75 psi
D. 100 psi
The correct answer is B There must be at least 50psi of refrigerant pressure in the system in order for a leak detector to be able to sense a leak. Refrigerant may have to be added to the system to achieve this.

11. A customer complains about a hissing noise coming from under the hood after turning off the car. A Technician says the noise is coming from the A/C system and is:
A. A normal condition
B. System pressures equalizing
C. Refrigerant leak
D. Both A and B
The correct answer is D The hissing noise is normal and caused by high-side pressure going through the refrigerant metering device as system pressures equalize.

12. The following are all methods of orifice tube replacement EXCEPT:
A. Replace the line that incorporates the orifice tube.
B. Disconnect the liquid line from the evaporator inlet line and pull the orifice tube straight out with an extractor tool.
C. Disconnect the liquid line from the evaporator inlet line and, using a twisting motion to break free of the line, pull out the orifice tube with an extractor tool.
D. Cut out the section of line containing the orifice tube and, using a kit, install a new orifice tube line segment.
The correct answer is C When removing the orifice tube with an extractor tool, do not twist or rotate the orifice tube in the line as it can break. If an orifice tube breaks during removal, special tools are available to extract broken orifice tubes. All of the other answers are methods of orifice tube replacement.

13. A customer has a complaint of poor heat output. After checking the hoses running from the heater
core and finding them both to be hot, Technician A says the problem could be a clogged heater core.
Technician B says a misadjusted temperature control cable 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 B If both hoses leading to the heater core are hot, coolant is circulating through the heater core. One hose that is significantly cooler than the other would indicate a clogged heater core. However, if the temperature control cable is incorrectly adjusted, the temperature blend door may not allow enough warm air to enter the passenger compartment for sufficient heating.

14. While identifying an A/C system, Technician A says that when the high-side service port fitting is smaller than the one on the low side, the system uses R134a refrigerant. Technician B says that an accumulator located between the evaporator and compressor is an indication that the system has an orifice tube. 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 Systems using an expansion valve have a receiver/drier between the valve and condenser, while orifice tube systems have an accumulator between the evaporator and compressor. Technician B is wrong because on R134a systems, the low-side service port is the smaller one.

15. Low heater output can be caused by all of the following EXCEPT:
A. Low coolant
B. A disengaged clutch type radiator fan
C. Plugged heater control valve
D. A stuck open cooling system thermostat
The correct answer is B A disengaged clutch cype radiator fan would not cause low heater output. All of the other answers are possible causes of low heater output.

16. During A/C system operation, a knocking sound can be heard coming from the compressor. Technician A says that there could be internal compressor damage. Technician B says that the compressor mounting brackets and bushings should be checked. 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 Knocking noises from the compressor usually indicate internal damage, especially on piston-type compressors. However, always check the compressor mounting and brackets before condemning the compressor for noise. A loose mounting can cause knocking noises from the compressor area that may be mistaken for internal compressor noise.

17. When using an electronic refrigerant leak detector, all of the following should be observed EXCEPT:
A. Leak detectors are very sensitive to many types of gases. If the area is contaminated with refrigerant or other gases, use a fan or compressed air to blow the excess refrigerant away.
B. Pass the probe around the top of components and hoses as refrigerant is lighter than air and tends to rise.
C. Don’t move the probe faster than one inch per second.
D. Never allow the probe to contact any surface, to prevent contamination of the sensing tip.
The correct answer is B Make sure that you pass the probe around the bottom of components and hoses as refrigerant is heavier than air and tends to settle.

18. An air conditioning check has uncovered a discharge in the system and compressor damage. Technician A says that after the repairs are made, to check the low-pressure cutoff switch. Technician B says lubricating oil is carried by the refrigerant through 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 purpose of the low-pressure cutoff switch is compressor protection. The compressor clutch circuit is opened if the pressure in the system drops too low. This would be an indication that the system has lost some or all of its refrigerant charge. Since the lubricating oil is carried by the refrigerant, a loss could cause damage to the compressor if it were allowed to operate without sufficient lubrication.

19. Which of the following is a true statement regarding R134a refrigerant?
A. It is harmful to the ozone layer.
B. It mixes with mineral oil.
C. It requires a different desiccant than R12.
D. It operates at lower pressures than R12.
The correct answer is C Desiccants are not universal and different types must be used with different refrigerants and lubricating oils. When a system is retrofitted, the replacement receiver/drier or accumulator has XH-7 or XH-9 desiccant.

20. To properly evacuate an A/C system, the vacuum pump should be operated a minimum of:
A. 5 minutes
B. 10 minutes
C. 20 minutes
D. 30 minutes
The correct answer is D To properly evacuate an A/C system, the vacuum pump should be operated for a minimum of 30 minutes.

21. Technician A says that the pressure cycling switch is usually located on the accumulator. Technician B says that the refrigerant must be recovered from the system before the switch can be removed. 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 The pressure cycling switch senses the low-side pressure near the evaporator outlet and is usually found on the accumulator. Technician B is wrong because the switch is often mounted in a schrader fitting so it can be replaced without the loss of refrigerant.

22. The inside of an EATC equipped vehicle never feels as cool as the temperature setting. The A/C system checks out OK, including the sensors. Technician A says the aspirator tube could be disconnected from the duct. Technician B says there could be an obstruction in the aspirator tube. 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 in-vehicle temperature sensor is located in the aspirator, which is located in the dashboard. The aspirator tube is connected to a heater-A/C duct. The air flowing in the duct past the tube creates a vacuum, drawing in-vehicle air past the sensor. If there is an obstruction in the aspirator tube or the tube is disconnected from the duct, air will not be drawn past the in-vehicle temperature sensor and the sensor will not be able to accurately measure the temperature inside the vehicle. This could account for the discrepancy between the temperature setting and the actual temperature inside the vehicle.

23. A vehicle with R134a refrigerant in the A/C system has a refrigerant leak. Technician A says that a propane gas leak detector should be used to find the location of the leak. Technician B says that an electronic leak detector should be used to check for leaks. 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 propane gas leak detectors cannot detect R134a. Technician B is right, but he must make sure the electronic leak detector is designed for R134a, as many older units are not.

24. The cooling fan works on low speed but not on high speed. Which of the following could be the
cause?
A. A faulty fan control resistor
B. An open in circuit 95S between the 95/95S splice and the high speed relay
C. A short to ground in circuit 95S between the 95/95S splice and the high speed relay
D. A blown 60 amp fuse
The correct answer is B The fan control resistor does not affect highspeed fan operation, therefore answer A is incorrect. A short to ground here will blow the 20-amp fuse and neither fan will work, therefore answer C is incorrect. If the 60-amp fuse is blown neither fan will work, therefore answer D is incorrect.

25. During an A/C system performance test, highside pressure was found to be excessive and the A/C
compressor continued to run. Technician A says that the high-pressure cutout switch could be defective. Technician B says that there could be an air flow obstruction at the condenser. 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 Both Technicians are correct. The high-pressure cutout switch should break the circuit to the compressor clutch if it detects pressures above a preset level. If the compressor continues to run when pressure passes the threshold of the switch calibration, the switch is defective. An obstruction to air flow through the condenser can also cause excessive highside pressure.

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.