ASE A7 Heating Air Conditioning Practice Test

11. An air conditioning system with a variable displacement compressor has poor performance in high demand situations. All of these could be the cause EXCEPT:

  • A. A low refrigerant charge.
  • B. A faulty control valve.
  • C. A faulty low pressure switch.
  • D. A weak compressor.

11.

Answer A is wrong. A low refrigerant charge would effect air conditioning performance.

Answer B is wrong. A faulty control valve would effect the air conditioner's performance.

Answer C is correct. A variable displacement compressor uses a control valve to alter system pressures. A cycling clutch orifice tube system has a pressure cycling switch on the low side of the system, often located on the accumulator.

Answer D is wrong. A weak compressor would result in poor performance.

12. Technician A says the clutch relay protects the control head from the clutch circuit's high current. Technician B says open clutch relay windings result in compressor clutch engagement at all times. Who is correct?

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

12.

Answer A is correct. Technician A is correct. A relay is a device used to protect control devices like PCM's from the high current used to power devices like an A/C clutch or a radiator fan.

Answer B is wrong. An open A/C relay will leave an A/C compressor's clutch inoperative.

Answer C is wrong. Technician A is correct.

Answer D is wrong. Technician A is correct.

13. All of these are true about an air conditioner's evaporator EXCEPT:

  • A. It removes humidity from the air.
  • B. Refrigerant flows from the bottom to the top.
  • C. Refrigerant enters the evaporator as a liquid.
  • D. The refrigerant changes from a vapor to a liquid as it receives heat from the cabin air.

13.

Answer A is wrong. The evaporator removes humidity from the air.

Answer B is wrong. The refrigerant flows from the bottom to the top.

Answer C is wrong. The refrigerant enters the evaporator core as a liquid.

Answer D is correct. The refrigerant converts from a liquid to a vapor, because it boils as it receives heat from the cabin air. Refrigerant has a very low boiling point.

Diagram of automotive ac control circuit.

14. The signal wire between the electronic climate control module and the low pressure sensor is:

  • A. Green with a yellow stripe.
  • B. Orange with a white stripe.
  • C. White with an orange stripe.
  • D. Orange with a red stripe.
Diagram of A/C climate controls.

14.

Answer A is wrong. According to the wiring diagram there is no green wire with a yellow stripe associated with the low pressure sensor.

Answer B is correct. The signal wire is orange with awhit e stripe.

Answer C is wrong. The ground wire is white with an orange stripe.

Answer D is wrong. The 5 volt reference wire is orange with a red stripe.

15. A blower motor operates only in high speed. Technician A says there could be a short in the motor's power feed. Technician B says it may have a faulty blower motor resistor. Who is correct?

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

15.

Answer A is wrong. A short in the motor's power feed would result in little or no operation in all selected speeds.

Answer B is correct. The blower resister's lower speeds share the same power source and offer varying resistance, while the high speed selection is on it's own circuit and has no resistors.

Answer C is wrong. Technician B is correct.

Answer D is wrong. Technician B is correct.