Service Flashcards
7 cards from real Air Conditioning Repair practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Service flashcards as text
When using an electronic leak detector on an air conditioning system, the probe should be moved:
Answer: Slowly along the bottom of fittings and connections
Refrigerant vapor is heavier than air and settles downward, so moving the probe slowly along the bottom of fittings ensures detection of leaking vapors.
A technician replaces a contactor on a condensing unit. After the repair, the compressor hums but does not start. What is the most likely cause?
Answer: Failed run capacitor
A humming compressor that won't start typically indicates a failed run or start capacitor that is not providing the necessary starting torque.
What is the correct procedure when adding refrigerant to a system equipped with a TXV metering device?
Answer: Charge by weight or target superheat at the evaporator outlet
TXV systems are best charged by weight per manufacturer specs or by targeting correct superheat, as sight glass clearing is not a reliable method for TXV systems.
Which component's failure would most likely cause high superheat AND high subcooling simultaneously?
Answer: Restricted liquid line or filter drier
A restriction in the liquid line or a clogged filter drier causes refrigerant to back up (high subcooling) before the restriction and starve the evaporator (high superheat) after it.
What does a nitrogen purge during brazing accomplish?
Answer: Prevents oxidation and carbon scale from forming inside the copper tubing
Flowing dry nitrogen through the tubing during brazing displaces oxygen, preventing the formation of copper oxides (scale) that can contaminate the system.
A split-system air conditioner has a normal suction pressure but an abnormally high discharge pressure. The MOST likely cause is:
Answer: Dirty or blocked condenser coil
A dirty condenser coil reduces heat rejection, causing refrigerant to remain at a higher temperature and pressure on the high side.
When is it acceptable to mix different types of refrigerant in a single system?
Answer: Never — mixing refrigerants is not permitted
Mixing different refrigerants creates an unidentified blend that cannot be safely recovered, recycled, or identified, and is prohibited by EPA regulations.