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 TXV-equipped system has low suction pressure and low superheat simultaneously. What is the MOST likely cause?
Answer: TXV stuck closed
A TXV stuck in the closed position starves the evaporator, causing low suction pressure; low superheat indicates little refrigerant is vaporizing past the valve.
What does a bubbling or foamy sight glass indicate in a refrigeration system?
Answer: Low refrigerant or liquid line restriction
Bubbles in the sight glass indicate the liquid refrigerant is flashing to vapor, which points to a low charge or restriction upstream.
A compressor that hums but fails to start most likely has a faulty:
Answer: Start capacitor or start relay
A failed start capacitor or start relay prevents the start winding from providing enough torque to overcome compressor inertia during startup.
Frost forming on the suction line all the way back to the compressor indicates:
Answer: Low superheat and possible liquid floodback
Suction line frost extending to the compressor indicates liquid refrigerant is returning, which can cause liquid slugging and compressor damage.
When recovering refrigerant from a system with a hermetic compressor burnout, the technician should:
Answer: Use a dedicated recovery cylinder and filter to avoid cross-contamination
Burnout contaminates refrigerant with acids and carbon; it must be recovered into a dedicated cylinder and sent for reclamation or disposal.
A refrigeration system loses capacity gradually over several weeks. The most cost-effective FIRST diagnostic step is to:
Answer: Check and record system operating pressures and temperatures
Measuring and recording operating pressures and temperatures provides a baseline to compare against design specs and identify the root cause systematically.
High condensing pressure accompanied by a hot condenser inlet and a cool condenser outlet MOST likely indicates:
Answer: Condenser coil fouled with dirt
A fouled condenser coil reduces heat transfer, causing high condensing pressure; the coil feels hot at the inlet but cool at the outlet because heat is not transferring through the dirty coil.