Thermostat shows "Heating" but only the blower runs, no warm 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 and gas (if applicable) before opening furnace panels. Gas and combustion issues can be hazardous.
Steps to check:
- Observe furnace LED codes: Restore power, call for heat, and watch the furnace control board LED for diagnostic flash codes. Refer to the furnace manual.
- Check gas supply: Ensure the gas shutoff valve near the furnace is open and that other gas appliances work.
- Reset furnace: Some furnaces have a manual reset for rollout or limit switches. Only reset if you understand the cause; repeated trips require professional service.
- Heat pump systems: If you have a heat pump, verify the outdoor unit runs when heat is called. If only the indoor fan runs, the issue is likely outside the thermostat.
When to call a pro: Burner, ignition, and high‑limit issues are furnace problems, not thermostat faults, and should be handled by a licensed HVAC technician.