Troubleshooting Flashcards
7 cards from real RSES practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Troubleshooting flashcards as text
A reciprocating compressor has low discharge pressure and low suction pressure, but the compressor runs continuously. What is the most likely fault?
Answer: Worn or leaking compressor valves
Worn or leaking compressor valves reduce pumping efficiency, resulting in low suction and discharge pressures with continuous runtime.
During a service call, a technician finds the evaporator fan running but no airflow over the coil. What is the most likely cause?
Answer: Evaporator coil completely iced over
A fully iced evaporator coil blocks airflow even when the fan motor is running and spinning.
A technician notices the suction line is frosting all the way back to the compressor. What condition does this indicate?
Answer: Flooded evaporator or excessive refrigerant flow
Frost extending to the compressor indicates liquid refrigerant is present in the suction line, meaning the evaporator is flooded.
Which instrument is used to measure superheat at the evaporator outlet?
Answer: A thermometer and manifold gauge set
Superheat is calculated by comparing the actual suction line temperature (thermometer) to the saturation temperature at suction pressure (manifold gauge).
A system has normal suction pressure but abnormally high discharge pressure. The condenser coils are clean. What should be suspected?
Answer: Non-condensable gases in the system
Non-condensable gases raise discharge pressure disproportionately because they do not condense and occupy condenser surface area.
What is the correct procedure to verify a restricted filter-drier in a liquid line?
Answer: Measure temperature drop across the drier and check for pressure drop
A temperature drop (and pressure drop if gauges are installed) across the drier indicates a restriction causing flash gas before the expansion device.
A heat pump in heating mode has low suction pressure but high discharge pressure. What is the most likely diagnosis?
Answer: Defective reversing valve causing partial bypass
A leaking reversing valve allows high-pressure discharge gas to mix with low-pressure suction gas, causing abnormal pressures in heating mode.