ASE A7 Heating Air Conditioning Practice Test

21. An EATC air conditioning system has low fan speed operation during high demand situations, like in direct sunlight. Technician A says this is because something is covering the sun load sensor's photo diode. Technician B says a sun load sensor is a variable resistor and can be tested with an ohmmeter. Who is correct?

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

21.

Answer A is wrong. The sun load sensor is a photo sensitive diode placed on the dash that changes resistance according to sun light.

Answer B is wrong. Many sensors in ATC or automatic temperature control systems are simple variable resistors that change resistance according to temperature.

Answer C is correct. Both technicians are correct.

Answer D is wrong. Both technicians are correct.

22. A gurgling sound is heard coming from inside the dashboard of a vehicle. Technician A says this is air trapped in the heater core. Technician B says this noise can be caused by a blown head gasket. Who is correct?

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

22.

Answer A is wrong. When air enters the heater core, a gurgling sound will occur.

Answer B is wrong. This condition can be caused by a blown head gasket forcing compression into the engine's cooling system.

Answer C is correct. Both technicians are correct.

Answer D is wrong. Both technicians are correct.

23. A manifold gauge indicates a system has low discharge pressure. The MOST likely cause of this condition is:

  • A. A restricted condenser.
  • B. A loose fan belt.
  • C. A damaged compressor reed valve.
  • D. A broken compressor piston.

23.

Answer A is wrong. A restricted condenser will result in high high side pressure.

Answer B is wrong. A loose fan belt will reduce air flow across the condenser, resulting in high high side pressure.

Answer C is correct. Damaged reed valves or plates result in low discharge pressure.

Answer D is wrong. A broken piston results in no compressor operation. A broken reed valve or plate assembly can result in a broken or damaged piston and cylinder.

24. The compressor is rapidly cycling on and off on a CCOT air conditioning system. Technician A says this condition can be caused by a low refrigerant charge. Technician B says this could be caused by a faulty clutch cycling switch. Who is correct?

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

24.

Answer A is wrong. A low system charge in a Cycling Clutch Orifice Tube system will result in rapid and continuous compressor clutch cycling.

Answer B is wrong. This pressure controlled switch closes to activate and opens to deactivate the compressor clutch.

Answer C is correct. Both technicians are correct.

Answer D is wrong. Both technicians are correct.

A/C Clutch Relay Circuit

25. There is a short to ground at point D of the electrical diagram above. Which of the following statements is true?

  • A. The clutch would not engage when powered.
  • B. The relay would remain open.
  • C. The PCM would not receive a signal from the clutch.
  • D. The clutch would engage whenever powered.

25.

Answer A is wrong. This circuit is controlled by the PCM. It grounds the relay resulting in compressor engagement.

Answer B is wrong. The relay would remain closed if there is a short to ground before the PCM. It would also likely blow the fuse.

Answer C is wrong. The clutch does not send a signal to the PCM.

Answer D is correct. The clutch would remain engaged when powered.