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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

  1. A technician finds oil staining around a brazed refrigerant joint on a rooftop unit. What should be done before adding refrigerant?

    Answer: Repair the leak, pressure-test, evacuate, then recharge

    EPA regulations require technicians to repair detectable leaks before recharging, followed by a pressure test and deep evacuation to ensure system integrity.

  2. An evaporative cooler delivers warm air despite the pump running. What is the MOST likely cause?

    Answer: Pads are mineral-scaled and restricting water distribution

    Heavily scaled or clogged evaporative pads prevent adequate water saturation, eliminating the evaporative cooling effect even when the pump operates.

  3. A geothermal heat pump shows high entering water temperature in cooling mode. What issue does this suggest?

    Answer: Undersized circulating pump or flow restriction in the ground loop

    High entering water temperature in cooling mode indicates the ground loop is not rejecting heat properly, usually due to inadequate flow from a weak pump or blockage.

  4. A rooftop unit's economizer damper stays open even when outdoor air enthalpy is high. What is the likely fault?

    Answer: Faulty enthalpy sensor or economizer controller

    An economizer that fails to close in high-enthalpy conditions points to a defective enthalpy sensor or a failed economizer control module that cannot signal the damper actuator.

  5. During a combustion analysis on a gas furnace, CO in the flue gas measures 600 ppm (air-free). What action is required?

    Answer: Immediately shut down the unit and tag it out pending heat exchanger inspection

    CO readings above 400 ppm air-free in flue gas indicate incomplete combustion likely caused by a cracked heat exchanger, which poses an immediate life-safety hazard.

  6. A packaged unit compressor makes a grinding noise on startup but runs quietly once at speed. What is the MOST likely cause?

    Answer: Failed start capacitor causing slow motor start

    A grinding or growling sound only during startup that resolves at speed is a classic sign of a weak start capacitor allowing the compressor motor to start slowly under high load.

  7. A technician measures static pressure drop across a filter at 0.65 in. w.c. on a system rated for 0.20 in. w.c. maximum. What is the expected outcome?

    Answer: Reduced airflow leading to low evaporator temperatures and potential coil icing

    Excessive filter restriction reduces airflow, causing the evaporator coil to drop below freezing temperature and eventually ice over, further compounding the restriction.