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 technician suspects a leaking discharge valve on a reciprocating compressor. Which test can confirm this?
Answer: Perform a pump-down test and observe suction pressure rise after shutdown
After pump-down, a rapid rise in suction pressure with the compressor off indicates high-pressure gas is leaking back through the discharge valve.
What is the purpose of installing a suction line accumulator on a refrigeration system?
Answer: To prevent liquid refrigerant from entering the compressor
A suction line accumulator traps liquid refrigerant and oil, allowing only vapor to enter the compressor, protecting it from liquid slugging.
A scroll compressor has normal amperage but produces no cooling. What should the technician check FIRST?
Answer: Phase rotation — scroll compressors must rotate in one direction
Scroll compressors operate in only one rotational direction; incorrect phase rotation causes the compressor to spin backwards, moving little or no refrigerant.
What condition is indicated when both suction and discharge pressures are abnormally low?
Answer: Large refrigerant leak or severe undercharge
When both pressures are low together, the system has lost a significant amount of refrigerant, reducing the overall pressure throughout the circuit.
A technician is troubleshooting an intermittent low-pressure lockout on a system. The MOST likely cause is:
Answer: Refrigerant leak that worsens under load
A slow refrigerant leak may not trip the low-pressure control at startup but causes suction pressure to drop below cutout as the system runs under load.
When a filter-drier becomes partially plugged, what is the MOST noticeable symptom?
Answer: Temperature drop across the filter-drier and bubbles in the sight glass
A plugged filter-drier creates a pressure drop that causes refrigerant to flash, resulting in a temperature drop across the drier and bubbles in the downstream sight glass.
Acid test results on refrigeration oil show high acid content. What is the CORRECT repair procedure?
Answer: Replace compressor oil, install suction and liquid line filter-driers, and monitor acid levels
High acid content indicates a burnout or severe contamination; the correct procedure is to replace the oil, install acid-rated filter-driers, and recheck acid levels after operation.