HVAC Troubleshooting Techniques 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 HVAC Troubleshooting Techniques flashcards as text
A heat pump runs continuously but fails to reach the set temperature in heating mode. What is the FIRST component to inspect?
Answer: Outdoor coil for ice buildup
A frozen outdoor coil severely restricts heat absorption and is the most common cause of a heat pump failing to heat adequately in cold weather.
A technician measures superheat of 25°F on a TXV-equipped system. What does this indicate?
Answer: TXV bulb may have lost its charge or TXV is underfeeding
High superheat on a TXV system typically points to a restricted or malfunctioning TXV that is underfeeding refrigerant to the evaporator.
During a gas furnace call for heat, the inducer motor starts but the ignitor never glows. Which component is most likely at fault?
Answer: Pressure switch
If the pressure switch fails to close after the inducer starts, the control board will not energize the ignitor because it has not confirmed proper draft.
An air conditioner short-cycles off on the high-pressure cutout. Outdoor ambient is 95°F and airflow over the condenser coil is adequate. What should the technician check next?
Answer: System refrigerant charge for overcharge
With adequate condenser airflow and high ambient, an overcharged system is the primary suspect for tripping the high-pressure cutout.
A customer reports their split system produces a musty odor whenever it runs. What is the most likely cause?
Answer: Microbial growth on the evaporator coil or drain pan
Musty odors from HVAC systems are almost always caused by mold or bacteria growing on the wet evaporator coil surface or standing water in the drain pan.
A variable refrigerant flow (VRF) system shows a communication error between the outdoor unit and one indoor unit. What is the FIRST diagnostic step?
Answer: Inspect the communication wiring for polarity, continuity, and loose connections
Communication errors in VRF systems are most commonly caused by wiring faults such as reversed polarity, broken conductors, or loose terminals rather than refrigerant or board issues.
A furnace control board locks out after three ignition attempts. The flame sensor reads 0.5 µA during a trial-for-ignition test with a visible flame. What is the problem?
Answer: Flame sensor is contaminated or coated with oxide
A flame sensor reading below 1–2 µA with a visible flame indicates the sensor rod is coated with oxidation or residue and cannot conduct enough current to prove flame.