Thermostat shows heat is on but only cool air blows from vents (with heat pump system)
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.
Possible Causes
How to Fix / Troubleshooting
Safety: Turn off power to indoor and outdoor units at the breaker before touching wiring.
- Verify heat pump configuration: In the Alexa app, confirm the system is set as a heat pump and that the O/B setting matches the outdoor unit (O = energized in cooling, B = energized in heating).
- Check O/B wiring: Ensure the reversing valve wire is connected to the O/B terminal at the thermostat and to the correct terminal at the air handler and outdoor unit.
- Test mode change: After correcting settings, switch between heat and cool and observe if the air temperature changes appropriately.
If wiring and configuration are correct but the system still blows cool air in heat mode, the outdoor reversing valve or its coil may be faulty; contact an HVAC technician.
Repair Difficulty
Required Part
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