ASE A7 Heating Air Conditioning Practice Test

Diagram of automotive ac control circuit.

41. Component A in the electrical diagram above has all of the following characteristics EXCEPT:

  • A. It is a Negative Temperature Coefficient sensor.
  • B. It is a thermistor.
  • C. It is a variable resistor.
  • D. It is a switch.

41.

ECT sensor

Answer A is wrong. An ECT sensor is an (NTC) Negative Temperature Coefficient sensor.

Answer B is wrong. An engine coolant temperature sensor is a thermistor.

Answer C is wrong. An engine coolant temperature sensor is a variable resistor that modifies a 5-volt reference signal from the control module. Resistors limit or control current flow (as well as voltage) in circuits.

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

42. A frozen spot is noticed in the center of the condenser. Technician A says frost on a component or connection indicates a restriction in the system. Technician B says this frost is caused by a clogged orifice tube. Who is correct?

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

42.

Answer A is correct. A restriction in a line or component acts as a metering device and changes the system's pressure. The change in pressure results in a change in temperature.

Answer B is wrong. A clogged orifice tube results in a frozen spot on the line containing the fixed orifice tube.

Answer C is wrong. Technician A is correct.

Answer D is wrong. Technician A is correct.

43. A vehicle's air conditioner only blows warm air, and a yellow substance is seen around the evaporator case drip tube. Technician A says this is coolant leaking from the heater core. Technician B says this is fluorescent dye leaking from the evaporator core. Who is correct?

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

43.

Answer A is wrong. Because poor air conditioning is the original problem, there is most likely a leak in the evaporator core.

Answer B is correct. Dye is injected into a system with hard to find leaks. The leak turns fluorescent yellow and is brought to light with a special light and glasses.

Answer C is wrong. Technician B is correct.

Answer D is wrong. Technician B is correct.

44. R 134a Refrigerant:

  • A. Changes from a vapor to a liquid as it absorbs heat.
  • B. Containers are sky blue colored.
  • C. Has a very high boiling point.
  • D. Contains chlorine.

44.

Answer A is wrong. R134a changes from a liquid to a vapor as it receives heat energy and boils in the evaporator.

Answer B is correct. An R134a refrigerant system has less refrigerant capacity than a similar R12 system. They also have different pressure characteristics. R134a is contained in a sky blue container, R-12 is contained in a white container.

Answer C is wrong. R134a has a very low boiling point.

Answer D is wrong. Answer B is correct.

45. A cooling system is losing coolant. A pressure test has been performed, and no leaks were found. Which of the following is MOST likely causing this condition?

  • A. A leaking water pump.
  • B. A faulty radiator pressure cap.
  • C. A leaking heater core.
  • D. A leaking radiator.

45.

Answer A is wrong. No external leaks were found. The radiator cap should be pressure tested.

Answer B is correct. A faulty radiator cap allows coolant to leak past its seal and overflow from the recovery system.

Answer C is wrong. Answer B is correct.

Answer D is wrong. Answer B is correct.