Daikin
Stuck Fan Relay / Fan On Due to Fault
Daikin furnace blower runs continuously even when there is no call for heat or fan from the thermostat.
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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
Fan set to ON at thermostat, Stuck blower relay on Daikin control board, Open high-limit switch causing fan-only operation, Shorted thermostat wiring between G and R
How to Fix / Troubleshooting
Safety: Turn off power before accessing the control board or thermostat wiring.
Steps to check:
- Thermostat setting: Verify the thermostat fan mode is set to AUTO, not ON.
- Check thermostat wiring: Remove the thermostat and inspect the wiring. Ensure G is not accidentally shorted to R or another terminal.
- Inspect high-limit: If the furnace recently overheated, the control may run the blower to cool the heat exchanger. Once cooled, the blower should stop. If it does not, the limit or board may be faulty.
- Board relay: On the Daikin control board, the blower relay may be stuck closed. If tapping the relay area lightly (with power off, then on) temporarily changes behavior, the board likely needs replacement.
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Repair Difficulty
Medium
3/5
Required Part
Daikin Furnace Main Control Board
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