Thermostat shows "Heat On" but heat pump runs in cooling mode (blowing cold air)
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 first: Turn off power to the air handler and outdoor heat pump at the breaker before adjusting wiring.
Steps to correct:
- Identify heat pump type: Check the outdoor unit documentation to see whether the reversing valve is energized in heating or cooling mode.
- Verify O/B configuration: In the Sensi installer menu, set the O/B option to match the manufacturer's requirement (energize in heat or cool).
- Check O/B wiring: Confirm the reversing valve wire is connected to the O/B terminal at the thermostat and to the correct terminal at the air handler or outdoor unit.
- Test operation: After changes, restore power and test both heating and cooling to ensure the correct mode is produced.
When to call a pro: If the system still runs in the wrong mode with correct configuration, the issue may be in the outdoor unit wiring or reversing valve coil, which requires HVAC service.