Compressor & Component Diagnostics Flashcards
7 cards from real CFC practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Compressor & Component Diagnostics flashcards as text
A scroll compressor exhibits abnormal noise during startup but runs quietly at full speed. What is the most likely cause?
Answer: Refrigerant slugging due to liquid floodback
Liquid refrigerant entering a scroll compressor during startup causes slugging noise as the incompressible fluid damages scroll wraps.
When diagnosing a reciprocating compressor with low suction pressure and low discharge pressure, which condition is most likely?
Answer: Worn or broken valve reeds
Broken or worn valve reeds cause low compression efficiency, resulting in both low suction and low discharge pressure simultaneously.
A technician measures a compressor's amp draw at 85% of the rated full-load amps with normal pressures. This indicates:
Answer: Normal operation within acceptable tolerance
Amp draw at 85% of rated FLA with normal pressures indicates the compressor is operating normally within standard tolerance bands.
What does a high superheat reading at the compressor suction combined with normal subcooling at the condenser outlet most likely indicate?
Answer: TXV or metering device starving the evaporator
High superheat with normal subcooling indicates insufficient refrigerant flow through the metering device, starving the evaporator of refrigerant.
A compressor trips on its internal overload repeatedly on hot days but resets overnight. The most probable diagnosis is:
Answer: High ambient temperature causing high head pressure overloading the motor
High ambient temperatures elevate condensing pressure, increasing compressor motor load and amp draw until the overload trips.
When performing a megohm test on a compressor motor, a reading of 0.5 megohms indicates:
Answer: Marginal insulation that may indicate moisture or contamination
A megohm reading of 0.5 MΩ indicates marginal insulation resistance, suggesting moisture contamination or degrading motor insulation.
A technician finds oil logged in the evaporator of a CFC system. Which compressor condition most commonly causes this problem?
Answer: Worn compressor rings allowing oil to bypass into the refrigerant circuit
Worn piston rings in a reciprocating compressor allow excessive oil to pass into the refrigerant stream, resulting in oil accumulation in the evaporator.