Troubleshooting & Repair Techniques Flashcards
7 cards from real CRST 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 & Repair Techniques flashcards as text
A heat pump in heating mode has frost building up on the outdoor coil when outdoor temperature is above 40°F. What is the MOST likely cause?
Answer: Low refrigerant charge reducing evaporating temperature
A low refrigerant charge drops the evaporating temperature below the frost point even in mild weather, causing premature frost accumulation on the outdoor coil.
A technician uses electronic leak detection and finds a leak at the evaporator coil. What is the NEXT step before brazing the repair?
Answer: Recover the refrigerant from the system
Before any brazing or open-flame work, refrigerant must be completely recovered to prevent combustion of refrigerant decomposition products and to comply with EPA regulations.
What is the MOST effective way to remove non-condensables from a refrigeration system?
Answer: Recover refrigerant, evacuate the system, and recharge with virgin refrigerant
Non-condensables cannot be separated in the field; the only correct method is full recovery, deep evacuation to remove air and moisture, and recharge with new refrigerant.
A compressor with a cracked discharge valve reed will MOST likely exhibit:
Answer: Low compression ratio and elevated suction pressure
A cracked discharge valve allows high-pressure gas to re-expand into the cylinder, reducing pumping efficiency and causing elevated suction pressure and low compression ratio.
When troubleshooting a system that repeatedly trips on high-pressure cutout, the technician should inspect the:
Answer: Condenser airflow, refrigerant charge, and non-condensables
High head pressure is caused by poor condenser heat rejection from blocked airflow, refrigerant overcharge, or non-condensables — all three must be checked.
A technician notices the suction pressure is pulsing rhythmically on the gauge. This is MOST often caused by:
Answer: TXV hunting due to improper superheat setting or bulb position
TXV hunting occurs when the valve over-corrects repeatedly, causing cyclic swings in suction pressure that appear as gauge pulsation.
After repairing a refrigerant leak and recharging a system, the technician should verify proper charge by checking:
Answer: Superheat or subcooling depending on the metering device type
Superheat is used to verify charge on fixed orifice systems, while subcooling is used on TXV systems; both methods confirm accurate refrigerant quantity in the circuit.