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Heat pump stuck in defrost or defrosting too long

Normal defrost lasts a few minutes, with the outdoor fan off, steam rising and aux heat on. A unit that stays in defrost points to a defrost thermostat/sensor that never opens, a board fault, or a reversing valve that doesn't shift back. Separate normal behaviour from a real fault first.

Cross-checked ~60 min advancedBrands: All

Before you start

  • Turn off the outdoor disconnect and verify 0 V before touching the board or wiring.
  • Remove any jumper as soon as the test is done.
  • Refrigerant checks (charge, gauges, valve replacement) are blocked: refer to an EPA 608-certified technician.

Diagnostic steps

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OnCall Tech is a reference tool for trained technicians and can make mistakes. Always disconnect power and confirm with the manufacturer's documentation before you work.

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Heat pump stuck in defrost or defrosting too long · OnCall Tech