Air Conditioning Repair Service 4 — Questions and Answers
Question 1: A technician measures a compressor's amp draw and finds it is above the rated full-load amps (FLA). Which condition would most likely cause this?
- High condensing temperature due to poor heat rejection (Correct answer)
- Low suction pressure from refrigerant undercharge
- Open run capacitor
- Low line voltage
Correct answer: High condensing temperature due to poor heat rejection
High condensing temperatures increase the pressure ratio the compressor must work against, forcing it to draw more current than its rated FLA.
Question 2: When evacuating a refrigeration system, the vacuum pump should be connected to:
- Both the high and low side service ports simultaneously (Correct answer)
- Only the low side service port
- Only the high side service port
- The suction line access port only
Correct answer: Both the high and low side service ports simultaneously
Connecting to both service ports ensures a faster, more complete evacuation by removing moisture and non-condensables from both sides of the system.
Question 3: What micron level must be achieved and held during system evacuation before charging with refrigerant?
- 500 microns or lower (Correct answer)
- 10,000 microns
- 2,000 microns
- 5,000 microns
Correct answer: 500 microns or lower
Industry standards require pulling the system down to 500 microns or lower and verifying the level holds to confirm adequate moisture removal and leak integrity.
Question 4: A homeowner reports that the AC runs constantly but never reaches the set temperature. After inspection, the technician finds the evaporator coil is clean and airflow is good. The NEXT diagnostic step should be:
- Measure system operating pressures and temperatures (Correct answer)
- Replace the thermostat immediately
- Add refrigerant without further diagnosis
- Increase blower speed
Correct answer: Measure system operating pressures and temperatures
Measuring operating pressures and temperatures provides the data needed to diagnose whether the issue is refrigerant charge, metering device, or compressor performance.
Question 5: Which tool is used to verify that a crankcase heater on a compressor is functioning properly?
- Clamp-style ammeter or infrared thermometer (Correct answer)
- Manifold gauge set
- Vacuum pump
- Refrigerant scale
Correct answer: Clamp-style ammeter or infrared thermometer
A clamp-style ammeter measures the small current draw of the crankcase heater, while an infrared thermometer confirms the heater is producing heat at the compressor base.
Question 6: What condition is indicated when the liquid line feels warm to the touch near the condenser on a properly charged system on a hot day?
- This is normal — the liquid line should be warm, carrying high-pressure liquid (Correct answer)
- The system is severely overcharged
- The condenser fan motor has failed
- The filter drier is restricted
Correct answer: This is normal — the liquid line should be warm, carrying high-pressure liquid
The liquid line carries high-pressure, warm liquid refrigerant from the condenser and will naturally feel warm to the touch under normal operation.
Question 7: A technician is servicing a heat pump in heating mode. Which component directs refrigerant flow to reverse the heating and cooling cycle?
- Reversing (four-way) valve (Correct answer)
- Check valve
- TXV with external equalizer
- Suction accumulator
Correct answer: Reversing (four-way) valve
The reversing valve (four-way valve) redirects refrigerant flow so the outdoor coil acts as the evaporator and the indoor coil acts as the condenser during heating mode.
Air Conditioning Repair Service 4
A technician measures a compressor's amp draw and finds it is above the rated full-load amps (FLA).
Which condition would most likely cause this?