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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 recovers refrigerant and finds the system has a deep vacuum after equalization. What does this indicate?

    Answer: The system had a leak and lost most of its charge

    A system that reaches a deep vacuum upon gauge connection has lost refrigerant through a leak, leaving sub-atmospheric pressure inside.

  2. A zoned HVAC system heats one zone but fails to condition a second zone. The zone 2 damper motor is receiving 24V. What should the technician check next?

    Answer: Mechanical damper blade for binding or disconnected linkage

    If the actuator has power but the damper does not move, the mechanical damper blade itself may be physically stuck, corroded, or the linkage arm may be detached.

  3. A mini-split indoor unit drips water onto the floor during cooling operation. What is the FIRST thing to inspect?

    Answer: Condensate drain line for blockage or improper slope

    Water dripping from a mini-split indoor unit almost always results from a blocked or improperly pitched condensate drain line that causes the drain pan to overflow.

  4. Subcooling reads 3°F on a fixed-orifice system operating in 80°F ambient. What condition does this suggest?

    Answer: Low refrigerant charge

    Very low subcooling on a fixed-orifice system indicates insufficient liquid refrigerant in the condenser, which is a sign of a low charge.

  5. A gas furnace pressure switch trips on every heating cycle after 10 minutes of operation. The inducer motor amperage is normal. What is the MOST likely cause?

    Answer: Blocked condensate drain causing water to back up into the pressure switch hose

    On high-efficiency condensing furnaces, condensate backing up into the pressure switch hose ports is a frequent cause of nuisance pressure switch trips after initial operation.

  6. An air handler blower runs on high speed only, regardless of the thermostat fan speed setting. What is the MOST likely cause?

    Answer: Failed ECM motor control module or incorrect dip-switch settings

    An ECM blower that ignores speed commands usually has a failed control module or incorrect programming/dip-switch configuration that defaults to maximum speed.

  7. A technician performs a nitrogen pressure test on a new refrigerant line set and observes pressure dropping from 300 psig to 285 psig over 15 minutes. What should the technician do?

    Answer: Locate and repair the leak before proceeding

    Any pressure drop during a nitrogen leak test indicates a leak that must be found and repaired before the system is evacuated and charged.