ASE ASE Heating & Air Conditioning 2 — Questions and Answers
Question 1: What is the purpose of the orifice tube in an automotive A/C system?
- Filters moisture from refrigerant
- Meters refrigerant flow into the evaporator (Correct answer)
- Compresses refrigerant vapor
- Stores refrigerant charge
Correct answer: Meters refrigerant flow into the evaporator
The orifice tube is a fixed metering device that restricts and meters refrigerant flow into the evaporator, causing a pressure drop.
Question 2: A heater core that leaks coolant into the passenger compartment will MOST likely cause which symptom?
- Overheating engine
- Sweet smell and fogged windows (Correct answer)
- Low coolant pressure
- No heat output only
Correct answer: Sweet smell and fogged windows
A leaking heater core deposits coolant inside the cabin, producing a sweet antifreeze odor and leaving a film on the windshield.
Question 3: What does a high reading on both the high-side and low-side A/C gauges MOST likely indicate?
- Refrigerant undercharge
- Blocked or restricted condenser (Correct answer)
- Stuck-open expansion valve
- Faulty compressor
Correct answer: Blocked or restricted condenser
A restricted condenser prevents heat rejection, causing both high-side and low-side pressures to rise above normal operating range.
Question 4: Which component controls the blend of heated and cooled air entering the passenger cabin in a dual-zone climate system?
- Blower motor resistor
- Blend door actuator (Correct answer)
- Recirculation door
- Evaporator temperature sensor
Correct answer: Blend door actuator
Blend door actuators position the blend door to mix heated air from the heater core and cooled air from the evaporator per thermostat settings.
Question 5: What is the correct procedure before adding refrigerant to an A/C system that has been opened for repair?
- Charge with refrigerant immediately
- Evacuate the system with a vacuum pump to remove moisture and air (Correct answer)
- Flush with nitrogen only
- Run the engine to purge lines
Correct answer: Evacuate the system with a vacuum pump to remove moisture and air
Evacuating the system pulls moisture out and creates a vacuum to confirm the system holds pressure before charging with refrigerant.
Question 6: Which sensor signal does the ECM primarily use to cycle the A/C compressor clutch on and off to protect the system?
- Ambient temperature sensor
- A/C pressure transducer (Correct answer)
- Evaporator outlet temperature sensor
- Engine coolant temperature sensor
Correct answer: A/C pressure transducer
The A/C pressure transducer sends system pressure data to the ECM, which disengages the compressor clutch if pressure is too high or too low.
ASE ASE Heating & Air Conditioning 2
What is the purpose of the orifice tube in an automotive A/C system?