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.
