Troubleshooting Flashcards
7 cards from real HVAC 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 flashcards as text
A technician finds high suction pressure and high discharge pressure with low superheat on an R-410A system. What is the most likely problem?
Answer: Refrigerant overcharge
Both elevated suction and discharge pressures combined with low superheat are classic signs of an overcharged refrigerant system.
An oil furnace fails to fire and the reset button on the primary control trips repeatedly. What should be checked first?
Answer: Fuel supply and oil filter condition
A clogged oil filter or empty fuel tank is the most common reason for repeated primary control lockout, as the burner cannot establish flame without adequate fuel.
A packaged rooftop unit produces insufficient cooling. Subcooling is 5°F and superheat is 18°F. What does this suggest?
Answer: Refrigerant undercharge
Low subcooling combined with elevated superheat indicates a refrigerant undercharge, reducing system capacity and efficiency.
A gas furnace produces a yellow, flickering flame. What is the most common cause?
Answer: Insufficient primary air to the burner
Insufficient primary air mixing with gas causes incomplete combustion, producing a yellow, sooty, or flickering flame instead of a clean blue flame.
After replacing a compressor, the system has high head pressure and high amp draw. The technician suspects what?
Answer: Non-condensables (air) in the system
Non-condensable gases like air raise head pressure significantly because they cannot condense, adding to the pressure burden on the compressor.
A split system AC cools well but the homeowner notices water dripping from the indoor unit. What is the most likely cause?
Answer: Clogged condensate drain
A clogged condensate drain prevents water from leaving the drain pan, causing it to overflow and drip from the air handler.
A heat pump compressor is noisy and the amp draw is high. Suction and discharge pressures are nearly equal. What has likely failed?
Answer: Compressor valve plates
Worn or broken compressor valve plates allow refrigerant to bypass, equalizing suction and discharge pressures and increasing amperage as the compressor struggles.