Air Conditioning Repair Service 2 — Questions and Answers
Question 1: When performing a refrigerant recovery, the technician should recover the refrigerant until the system pressure reaches:
- 0 psig or as low as possible (Correct answer)
- 10 psig
- 30 psig
- 50 psig
Correct answer: 0 psig or as low as possible
EPA regulations require recovering refrigerant to 0 psig or as low as the recovery machine can achieve to minimize emissions.
Question 2: A technician notices that the evaporator coil is icing up during operation. Which service step should be performed FIRST?
- Check airflow across the evaporator (Correct answer)
- Add refrigerant to the system
- Replace the TXV
- Clean the condenser coil
Correct answer: Check airflow across the evaporator
Restricted airflow is the most common cause of evaporator icing, and checking it first eliminates the simplest root cause before invasive repairs.
Question 3: What is the purpose of performing a standing pressure test on a system after repair?
- To verify no leaks exist before charging with refrigerant (Correct answer)
- To check compressor capacity
- To measure superheat
- To calibrate the thermostat
Correct answer: To verify no leaks exist before charging with refrigerant
A standing pressure test uses dry nitrogen to verify system integrity and confirm no leaks are present before introducing refrigerant.
Question 4: Which oil is required for use in systems containing R-410A refrigerant?
- POE (polyolester) oil (Correct answer)
- Mineral oil
- Alkylbenzene oil
- PAG oil
Correct answer: POE (polyolester) oil
R-410A systems require POE (polyolester) oil because it is miscible with HFC refrigerants, ensuring proper lubrication throughout the system.
Question 5: During a service call, a technician measures suction pressure lower than normal and discharge pressure lower than normal. This most likely indicates:
- Low refrigerant charge (Correct answer)
- High refrigerant charge
- Dirty condenser coil
- Faulty reversing valve
Correct answer: Low refrigerant charge
Both suction and discharge pressures below normal simultaneously is a classic indicator of an undercharged (low refrigerant) system.
Question 6: Before replacing a compressor, a technician should always:
- Perform a system flush to remove contaminants (Correct answer)
- Increase the refrigerant charge by 10%
- Replace only the run capacitor
- Bypass the high-pressure switch
Correct answer: Perform a system flush to remove contaminants
Flushing removes acid, moisture, and debris from a failed compressor before installing a new one, preventing premature failure of the replacement.
Question 7: A technician is checking subcooling on a fixed-orifice system. Where should subcooling be measured?
- At the liquid line service valve near the condenser outlet (Correct answer)
- At the suction line near the compressor
- At the discharge line near the compressor
- At the inlet of the evaporator
Correct answer: At the liquid line service valve near the condenser outlet
Subcooling is measured at the liquid line leaving the condenser, comparing the actual temperature to the saturation temperature at that pressure.
Air Conditioning Repair Service 2
When performing a refrigerant recovery, the technician should recover the refrigerant until the system pressure reaches: