Day & Night
Defrost Cycle Failure (Heat Pump)
Heat pump blows cool air in heating mode; outdoor unit may be iced over
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Safety Warning
This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.
If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.
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Possible Causes
Failed defrost sensor, Faulty defrost control board, Stuck reversing valve, Outdoor fan not running during defrost
How to Fix / Troubleshooting
Safety first: Turn OFF power at the outdoor disconnect before servicing. Do not chip ice off the coil with sharp tools.
- Step 1 – Inspect outdoor coil: If heavily iced, switch system to EMERGENCY HEAT (if available) and turn OFF the outdoor unit to allow thawing.
- Step 2 – Check defrost sensor and wiring: Ensure the sensor is attached and wiring is intact.
- Step 3 – Observe defrost operation: With power restored, a technician can force a defrost cycle to verify board and valve operation.
- Professional repair: Defrost control and reversing valve issues require a qualified HVAC technician.
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Repair Difficulty
Professional Required
5/5
Required Part
Defrost Control Board
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