ASE A7 Heating Air Conditioning Practice Test

36. A CCOT system has a high high side. Technician A says to suspect the thermostatic expansion valve. Technician B says this system contains an orifice tube. Who is correct?

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

36.

Answer A is wrong. A thermostatic expansion valve is not used on (CCOT) cycling clutch orifice tube systems, it's used with TXV systems. CCOT systems use a fixed metering device; a (FOT) fixed orifice tube. An expansion valve meters refrigerant into the evaporator core according to temperature.

Answer B is correct. A clogged orifice tube will result in high high side pressure. It can become clogged with contaminants, debris from a damaged compressor, or a broken desiccant bag releasing desiccant into the refrigerant.

Answer C is wrong. Technician B is correct.

Answer D is wrong. Technician B is correct.

Diagram of automotive ac control circuit.

37. Corrosion at point A of the electrical diagram above will result in:

  • A. Excessive resistance in the splice leading to the high pressure sensor.
  • B. Voltage drop at the connector of the signal circuit for the high pressure sensor.
  • C. Excessive resistance in the reference circuit of the high pressure sensor.
  • D. Voltage drop at the connector of the ground circuit for the high pressure sensor.

37.

Answer A is wrong. The symbol indicates that component is a connector not a splice.

Answer B is correct. This is a three wire sensor. From left to right there is a ground circuit, then the signal circuit back to the control module, and the third is the 5 volt reference circuit.

Answer C is wrong. The signal circuit's connector is corroded.

Answer D is wrong. It's a sensor, A/C systems use switches that are either open or closed. They don't modify reference signals like sensor's do.

38. A vehicle's air conditioning performance is reduced at low speeds and stop lights, but cools at highway speeds. Which of these is MOST likely causing this condition?

  • A. A low refrigerant charge.
  • B. A missing fan shroud.
  • C. A missing air dam.
  • D. A faulty compressor clutch relay.

38.

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

Answer B is correct. A properly fitting and fastened fan shroud is vital for good A/C and engine performance. Many of these shrouds and dams create a low pressure area behind the radiator and condenser. Loose or missing shrouds will be especially noticeable as the vehicle slows and ram air is reduced.

Answer C is wrong. Air dams help cool the radiator and condenser at highway speeds. Removing the air dam would reduce air flow at higher speeds, not lower speeds.

Answer D is wrong. A weak compressor will result in poor A/C performance at all times.

39. Two technicians are discussing an inoperative electric blend door in an automatic air conditioning system. Technician A says to inspect the blend door's wiring and connections for an open circuit. Technician B says to troubleshoot this circuit with a test light. Who is correct?

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

39.

Answer A is correct. An open in the circuit would prevent the blend door's motor operation.

Answer B is wrong. Use a high-impedance multimeter to test today's sensitive computer circuits. A standard test light can draw too much current, resulting in damage to sensitive components.

Answer C is wrong. Technician A is correct.

Answer D is wrong. Technician A is correct.

40. An air conditioner with an expansion valve performs poorly only during the hottest times of the day. Technician A says the receiver drier may be saturated. Technician B says there may be moisture in the refrigerant. Who is correct?

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

40.

Answer A is wrong. Both technicians are correct.

Answer B is wrong. Both technicians are correct.

Answer C is correct. The receiver drier contains a desiccant that must be changed after it's been exposed to moisture. If saturated with moisture, the excessive moisture in the drier will flow to the expansion valve and freeze, reducing system performance. Poor system performance is most noticeable during the hottest times of the day.

Answer D is wrong. Both technicians are correct.