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error Honeywell
Error Code Aux heat runs in cooling
Auxiliary heating activates when system is in cooling mode, causing conflicting operation.
? What Causes This
Wire incorrectly attached to W terminal on UWP in heat pump systems.
✓ How to Fix It
- Verify wiring configuration for heat pump systems.
- Ensure no wire is attached to the W terminal on UWP.
- Consult 'Wiring heat pump systems' section on page 4 for correct configuration.
Source: page 10 of the official manual
From the manual
This error code appears in:
Honeywell T3 Pro Programmable Thermostat