ASE A7 Heating Air Conditioning Practice Test

16. A compressor clutch coil is being tested. There is 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 A and B
  • D. Neither A or B

16.

Answer A is wrong. 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.

Answer B is correct. 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.

Answer C is wrong. Technician B is correct.

Answer D is wrong. Technician B is correct.

17. 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 condition is:

  • A. An overheating engine.
  • B. A weak electric fan motor.
  • C. A frozen expansion valve.
  • D. Debris in the condenser fins.

17.

Answer A is wrong. Excessive engine heat affects the condenser's ability to transfer heat to the atmosphere.

Answer B is wrong. While the vehicle is traveling forward, 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.

Answer C is correct. This is a least likely type question. Once the expansion valve freezes, the air conditioning would have poor performance at all speeds.

Answer D is wrong. Debris on the condenser's fins reduces the ability of the condenser to transfer heat. This is even more pronounced when the vehicle is at rest.

18. The carpet is wet on the passenger's side of a vehicle. Technician A says this may be caused by a leaking heater core. Technician B says this could be caused by a clogged evaporator case drain tube. Who is correct?

  • A. Technician A
  • B. Technician B
  • C. Both A and B
  • D. Neither A or B

18.

Answer A is wrong. A leaking heater core will result in coolant leaking on to the passenger's carpet. It can result in a sweet smell in the front passenger compartment.

Answer B is wrong. A clogged drip tube will result in condensation collecting in the evaporator case and dripping into the passenger compartment.

Answer C is correct. Both technicians are correct.

Answer D is wrong. Both technicians are correct.

19. The in-cabin temperature sensor is suspected for an air conditioner's poor performance. Technician A says the in-cabin temperature sensor is a NTC that should be tested for resistance with an ohmmeter. Technician B says the aspirator may be disconnected from the vent system. Who is correct?

  • A. Technician A
  • B. Technician B
  • C. Both A and B
  • D. Neither A or B

19.

Answer A is wrong. The in-cabin or in-car temperature sensor is a NTC or negative temperature coefficient sensor that can be tested for resistance with an ohmmeter. Both technicians are correct.

Answer B is wrong. An aspirator is used to create the suction necessary to create air flow through the sensor. Small electric fans are also used to gather cabin air temperature samples.

Answer C is correct. Both technicians are correct.

Answer D is wrong. Both technicians are correct.

20. A (TXV) thermostatic expansion valve system blows cold air for five minutes and then goes warm. Technician A says this condition is caused by a low refrigerant charge. Technician B says this condition is caused by moisture in the system. Who is correct?

  • A. Technician A
  • B. Technician B
  • C. Both A and B
  • D. Neither A or B

20.

Answer A is wrong. A low refrigerant charge will result in poor performance at all times.

Answer B is correct. After a few minutes moisture freezes in the expansion valve restricting refrigerant from entering the evaporator core. A saturated receiver drier will result in this condition.

Answer C is wrong. Technician B is correct.

Answer D is wrong. Technician B is correct.