ASE A7 Heating Air Conditioning Practice Test

1. During a performance test on a CCOT A/C system, the manifold gauge set indicates that the low side pressure is high, and the high side pressure is low. These test results indicate:

  • A. A frozen expansion valve.
  • B. A bad compressor.
  • C. A restricted condenser.
  • D. A clogged receiver drier.

1.

Answer A is wrong. Thermostatic expansion valves meter refrigerant in TXV air conditioning systems. A CCOT (cycling clutch orifice tube) system has a fixed orifice tube that meters a fixed amount of refrigerant.

Answer B is correct. A high low side and a low high side indicates a faulty A/C compressor, whether it is a CCOT (cycling clutch orifice tube), or a TXV (thermostatic expansion valve) system.

Answer C is wrong. A restricted or clogged condenser results in high discharge pressure.

Answer D is wrong. A receiver drier cleans and removes moisture from the refrigerant in TXV thermostatic expansion valve systems.

2. A vehicle's passenger heating system is set to MAX HEAT but blows warm air only. All of the following will cause this condition EXCEPT:

  • A. An air pocket in the heater core.
  • B. A restricted heater control valve.
  • C. A weak engine cooling fan motor.
  • D. A clogged heater core.

2.

Answer A is wrong. An air pocket in the heater core reduces performance and results in a gurgling sound under the dash.

Answer B is wrong. A restricted heater control valve results in low heater performance.

Answer C is correct. A weak engine cooling fan motor results in engine overheating and poor air conditioning performance.

Answer D is wrong. A clogged heater core blocks flow, affecting the system's performance.

3. The fixed orifice tube is removed from the high side of a CCOT air conditioning system. Metal debris is clogging the inlet screen. This metal debris is MOST likely caused by:

  • A. A ruptured desiccant bag.
  • B. The evaporator core.
  • C. A worn compressor.
  • D. The condenser.

3.

Answer A is wrong. Gummy or gooey debris in the orifice tube's inlet filter is usually a ruptured desiccant bag from inside of the accumulator.

Answer B is wrong. The evaporator core is not likely causing the metal debris.

Answer C is correct. Metal debris in the orifice tube's inlet filter is most likely caused by compressor wear.

Answer D is wrong. The condenser is not likely causing metal debris. Flush the system and replace any faulty components.

4. Technician A says an expansion valve reduces refrigerant pressure as it enters the evaporator core. Technician B says the expansion valve is fastened to the inlet port of the evaporator core. Who is correct?

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

4.

Answer A is wrong. There are two types of metering devices used in today's vehicles; the (TXV) thermostatic expansion valve and the (FOT) fixed orifice tube.

Answer B is wrong. An externally equalized expansion valve is fastened to the inlet port of the evaporator, and the sensing bulb is fastened on the outlet port.

Answer C is correct. Both technicians are correct.

Answer D is wrong. The gas inside the sensing bulb expands as the temperature increases, causing the diaphragm to move a pintle, allowing refrigerant to enter the evaporator.

Diagram of automotive ac control circuit.

5. All of the following are true about the air temperature blend door in the circuit illustrated above EXCEPT:

  • A. It has a microchip and logic.
  • B. It operates on CAN Class A network.
  • C. The actuator contains a microchip and logic.
  • D. It operates on the CAN protocol.

5.

Answer A is wrong. Each motor has a unique ID. An actuator with a lower ID has priority over an actuator with a higher ID.

Answer B is correct. There are three speeds. Class A is the slowest. The climate control network is typically on a Class B network with speeds up to 125 Kbps. Class C CAN operates at speeds up to 1 Mbps for engine and transmission critical sensor data.

Answer C is wrong. Each motor has a unique ID. An actuator with a lower ID has priority over an actuator with a higher ID.

Answer D is wrong. Vehicles manufactured in 2008 and up contain networks that operate on the CAN protocol.