Gibson
Continuous Fan Operation
Blower runs continuously even when thermostat is not calling for heat or fan
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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 switch set to ON at thermostat, Stuck blower relay on Gibson control board, Limit switch stuck open causing fan-only mode, Shorted G (fan) wire to R
How to Fix / Troubleshooting
Safety first: Turn off power before removing furnace panels.
Steps to check:
- Thermostat fan setting: Ensure the fan is set to AUTO, not ON.
- Check G wire: Inspect thermostat cable for damage. At the furnace, remove the G wire from the control board. If the blower stops after a short delay, the thermostat or wiring is causing the fan call.
- Limit switch: If the high limit is open, many Gibson furnaces will run the blower continuously. Check for a limit fault code and address overheating causes.
- Control board: If blower runs even with G disconnected and no limit fault, the blower relay on the board may be stuck and the board will need replacement.
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Repair Difficulty
Medium
3/5
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