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.
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.
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.
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
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.
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.
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.