Heating and Air Conditioning Flashcards
7 cards from real NAPA practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Heating and Air Conditioning flashcards as text
With the A/C running, gauges show low-side pressure higher than normal and high-side pressure lower than normal. What is the most likely cause?
Answer: Worn or failing compressor
A compressor with internal leakage can't build head pressure, so the low side reads high and the high side reads low.
Both low-side and high-side pressures read higher than specification, and the condenser fan is working. What should be checked next?
Answer: Refrigerant overcharge or debris blocking the condenser fins
Too much refrigerant or poor heat rejection at the condenser raises pressure on both sides.
On an orifice tube system, frost forms on the liquid line just ahead of the orifice tube and both pressures are low. What is indicated?
Answer: Restricted orifice tube
A restriction causes a pressure drop and cooling at the blockage point, producing frost there.
A system cools well for a while, then blows warm air, then cools again after being shut off. What is the most likely cause?
Answer: Moisture in the system freezing at the metering device
Moisture freezes at the expansion valve or orifice and blocks flow, then thaws when the system is off.
Before connecting a recovery machine to a vehicle with unknown refrigerant history, what should the technician do first?
Answer: Use a refrigerant identifier to check purity
An identifier prevents contaminated or mixed refrigerant from entering and ruining the shop's recovery equipment and supply.
With the engine off and the system at rest for several hours, static gauge pressure on both sides should roughly match what?
Answer: The pressure corresponding to ambient temperature on a P/T chart
At rest, the refrigerant equalizes and its pressure matches the saturation pressure for the surrounding temperature.
An electronic leak detector is being used to find a slow leak. Where should the probe be moved most carefully, and why?
Answer: Below fittings, because refrigerant is heavier than air
Refrigerant vapor is heavier than air, so it settles below the leak point.