EPA 609 Leak Detection & System Diagnosis 1 — Questions and Answers
Question 1: Which tool is specifically designed to detect refrigerant leaks in an MVAC system?
- Manifold gauge set
- Electronic leak detector (Correct answer)
- Vacuum pump
- Refrigerant identifier
Correct answer: Electronic leak detector
An electronic leak detector is designed to sense refrigerant vapors and alert the technician to the presence of a leak.
Question 2: What does a manifold gauge reading of 0 psi on BOTH the high and low sides most likely indicate?
- The system is properly charged
- The compressor is functioning normally
- The system has lost all refrigerant charge (Correct answer)
- The expansion valve is stuck open
Correct answer: The system has lost all refrigerant charge
Zero pressure on both sides means the system has no refrigerant remaining, indicating a total loss of charge due to a major leak or prior incomplete service.
Question 3: UV dye is injected into an MVAC system primarily to:
- Lubricate the compressor seals
- Identify refrigerant leaks under ultraviolet light (Correct answer)
- Improve system cooling efficiency
- Neutralize moisture contamination
Correct answer: Identify refrigerant leaks under ultraviolet light
UV dye circulates with the refrigerant and oil, and when a leak occurs, dye seeps out and glows brightly under a UV lamp, pinpointing the leak location.
Question 4: An MVAC system that blows warm air while the compressor is running could indicate:
- Excessive refrigerant charge
- A refrigerant leak causing low charge (Correct answer)
- A faulty blower motor resistor
- Incorrect blend door calibration
Correct answer: A refrigerant leak causing low charge
A refrigerant leak reduces system charge, lowering refrigerant flow and heat absorption, so the evaporator cannot cool adequately even though the compressor runs.
Question 5: Frost or ice forming on the orifice tube or expansion valve in an MVAC system usually signals:
- Normal refrigerant flow at high ambient temperatures
- A restriction or moisture contamination causing a pressure/temperature drop (Correct answer)
- Overcharge of refrigerant
- A faulty condenser fan motor
Correct answer: A restriction or moisture contamination causing a pressure/temperature drop
A restriction or moisture freeze at the metering device causes a dramatic pressure and temperature drop immediately downstream, leading to ice formation.
Question 6: When using an electronic leak detector, the probe should be moved:
- Quickly across large areas to cover more ground
- Slowly along the bottom of hoses and fittings since refrigerant vapors are heavier than air (Correct answer)
- Only around the compressor shaft seal
- Above all system components since refrigerant vapors rise
Correct answer: Slowly along the bottom of hoses and fittings since refrigerant vapors are heavier than air
Most automotive refrigerants are heavier than air and settle downward, so probing slowly beneath hoses, fittings, and connections increases detection sensitivity.
Question 7: Before performing a leak check on an MVAC system, the technician should first:
- Evacuate the system completely
- Run the A/C for several minutes to pressurize all components (Correct answer)
- Add refrigerant until the system is fully charged
- Disable the compressor clutch relay
Correct answer: Run the A/C for several minutes to pressurize all components
Operating the system pressurizes the entire refrigerant circuit, making leaks more detectable because refrigerant is forced through any gaps or cracks under pressure.
EPA 609 Leak Detection & System Diagnosis 1
Which tool is specifically designed to detect refrigerant leaks in an MVAC system?