Day & Night
Stuck Fan On / No Heat Call
Furnace blower runs but burners never light; cool air blows continuously.
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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.
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Possible Causes
Thermostat fan set to ON, stuck fan relay on control board, shorted G (fan) thermostat wire to R
How to Fix / Troubleshooting
Safety first: Turn off power before accessing wiring.
- Thermostat setting: Check that the thermostat fan mode is set to AUTO, not ON, if you only want heat when needed.
- Inspect thermostat wiring: Remove the thermostat and inspect the G and R wires. Ensure they are not touching or shorted together.
- Control board check: With power OFF, inspect the control board for signs of burnt fan relay. If the blower runs even with the G wire disconnected at the board, the relay is likely stuck.
A stuck fan relay requires control board replacement by a technician.
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Repair Difficulty
Medium
3/5
Required Part
Integrated Furnace Control Board
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