Safety: Turn OFF power at the outdoor disconnect before servicing the condenser.

Visual inspection: Check the outdoor coil for heavy frost or ice buildup. If the coil is encased in ice, the defrost cycle is not working properly.
Check outdoor fan: In heat mode, confirm the outdoor fan runs. If not, troubleshoot the fan motor and capacitor as previously described.
Verify coil sensor: Inspect and test the outdoor coil sensor as in H2. Replace if defective.
Defrost board check: Inspect the defrost control board for burnt components or water damage. Ensure all connectors are seated.
Reversing valve operation: Listen for the reversing valve shifting when switching between heat and cool. If it does not shift and wiring is correct, the valve or coil may be faulty.
Professional service: If H3 persists after sensor and fan checks, a technician should test the defrost board logic and reversing valve operation.

Note: Do not attempt to manually chip ice off the coil; allow it to melt naturally or use warm air.

Coleman heat pump air conditioner shows H3 and may shut down heating operation during cold weather.

Possible Causes