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 heat pump is running in heating mode but the discharge air feels cool. What is the most likely cause?
Answer: Reversing valve stuck in cooling position
A reversing valve stuck in the cooling position causes the heat pump to pump heat outdoors instead of indoors, resulting in cool discharge air during heating mode.
An air conditioner short-cycles (turns on and off frequently). Which of the following is the LEAST likely cause?
Answer: Dirty evaporator coil
A dirty evaporator coil typically causes the unit to run longer or freeze up, not short-cycle; oversized equipment, low charge, and faulty contactors are common short-cycling causes.
A technician measures suction pressure of 55 psig and discharge pressure of 175 psig on an R-22 system. What condition does this indicate?
Answer: Low refrigerant charge
Low suction and low discharge pressures on an R-22 system indicate a refrigerant undercharge, reducing the system's capacity.
A gas furnace ignites but the burner shuts off after a few seconds. What component is most likely faulty?
Answer: Flame sensor (flame rod)
A dirty or failed flame sensor cannot verify the presence of a flame, causing the control board to shut off gas flow as a safety measure.
A condensate drain line is clogged on a high-efficiency furnace. What symptom would you expect?
Answer: Unit shuts down on pressure switch lockout
A clogged condensate drain causes water to back up and block the pressure switch port, causing the furnace to lockout on a pressure switch fault.
Which tool is used to confirm that a compressor motor winding is not grounded to the compressor shell?
Answer: Megohmmeter (megger)
A megohmmeter applies high voltage to measure insulation resistance, confirming whether a winding is grounded to the compressor shell.
An evaporator coil repeatedly freezes. After verifying adequate airflow, the next most likely cause is:
Answer: Low refrigerant charge
Low refrigerant charge reduces suction pressure and evaporator temperature below the freezing point of moisture in the air, causing coil icing.