ASE A7 Heating Air Conditioning Practice Test
21. A vehicle with a CCOT air conditioning system has a low refrigerant charge. All of the following should be leak tested EXCEPT:
- A. The clutch cycling switch.
- B. The condenser.
- C. The evaporator core.
- D. The expansion valve.
Answer A is wrong. A cycling clutch switch engages and disengages the compressor clutch according to the system's low side pressure. The pressure cycling switch is located on the accumulator or the low side of a system.
Answer B is wrong. Test the condenser for leaks.
Answer C is wrong. Test the evaporator core for leaks.
Answer D is correct. All the others are correct EXCEPT answer D. (FOT) fixed orifice tubes meter refrigerant in (CCOT) Cycling Clutch Orifice Tube systems. An expansion valve is found on and meters refrigerant in a (TXV) Thermostatic Expansion Valve system.
22. The compressor's clutch functions normally at idle but disengages whenever the engine is accelerated. Which of the following is correct?
- A. The (TPS) throttle position sensor is faulty or out of adjustment.
- B. The compressor clutch relay is faulty and sticking in the closed position.
- C. Answers A and B are both correct.
- D. Answers A and B are both wrong.
Answer A is correct. The TP sensor detects the engine's load by indicating the throttle plate's angle to the ECM. It should not disengage the compressor at idle or during normal acceleration.
Answer B is wrong. A stuck closed relay results in continuous operation. When the control module receives a WOT or wide-open throttle signal from the TP sensor, it signals the clutch relay to disengage the compressor clutch.
Answer C is wrong. The compressor consumes a small amount of horsepower; to increase power at wide open throttle, the ECM opens the A/C clutch relay to disengage the clutch.
Answer D is wrong. The TP sensor is attached to the throttle plate shaft and changes output voltage as the throttle plate opens and closes. The output voltage is low or around 0.45 volts when the throttle is closed and is high or 4.5 volts at WOT.
23. Which of the following statements is correct about component A in the diagram above?
- A. It is a two position actuator.
- B. It is an outside recirculation door.
- C. It provides feedback to the controller.
- D. It contains a vacuum motor.
Answer A is wrong. It's a variable-position actuator. Automatic and semiautomatic air conditioning systems use electric motors that provide feedback on the blend doors position in real-time.
Answer B is wrong. It's a blend door motor that contains a potentiometer, a type of variable resistor.
Answer C is correct. The controller uses voltage reversal to drive the motor back and forth. It's able to check the actual position of the blend door with a potentiometer located inside the motor assembly.
Answer D is wrong. Automotive air conditioning systems contain different electric door actuators (motors) that blend and distribute air through the duct system and into the passenger compartment. These actuators have replaced or work in unison with vacuum motors and Bowden cables.
24. During the initial inspection, a spot of frost appears on the condenser's fins. Which of the following is correct?
A. There is a restriction at that point of the condenser.
B. A restriction in the condenser results in low high-side pressure readings.
- A. Answer A
- B. Answer B
- C. Both A and B
- D. Neither A or B
Answer A is correct. Observe the condenser's condition and look for creases or damage from flying road debris. A crease or restriction in a condenser appears as ice or frost forming around the area.
Answer B is wrong. A restriction in an automotive air conditioning condenser results in high high side discharge pressures.
Answer C is wrong. The condenser receives high-temperature, high-pressure vapor from the compressor. The heat contained in the refrigerant passes through the condenser's fins into the atmosphere.
Answer D is wrong. A non-contact infrared thermometer can be used to check for restrictions. The conversion in temperature from top to bottom should be smooth and even.
25. An engine with a viscous fan clutch makes a whirring noise that increases with engine speed. Which of the following is MOST likely causing this condition?
- A. A damaged fan blade.
- B. Worn water pump bearings.
- C. A stuck/frozen fan clutch.
- D. A leaking fan clutch.
Answer A is wrong. Check for cracks and excessive wear, especially in plastic fan blades. They provide airflow through the radiator fins, transferring heat from the engine's coolant to the outside air.
Answer B is wrong. Bent or missing blades cause an imbalance, damaging the water pump's bearings and seals.
Answer C is correct. A stuck/frozen viscous fan clutch makes a whirring sound that increases with engine speed.
Answer D is wrong. A viscous fan clutch contains silicon oil that can leak from the unit. The viscosity of this thick fluid is measured in CST or centistokes and wears over time. Check the unit for leaks through the seams and around the shaft.