Thermo Pride
Stuck Fan Relay or Open Limit Circuit
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 relay stuck closed on Thermo Pride control board, Thermostat fan set to ON, Open high limit switch forcing continuous blower, Shorted G (fan) thermostat wire
How to Fix / Troubleshooting
Safety First: Turn off power before removing furnace panels.
- Check thermostat fan setting: Ensure it is set to AUTO, not ON.
- Disconnect G wire test (advanced): With power off, remove the G wire from the control board. Restore power. If the blower stops, the thermostat or wiring is calling for fan.
- Inspect high limit switch: If the limit is open, some boards run the blower continuously. A technician should test and replace the limit if faulty and correct any overheating cause.
- Control board relay: If the blower runs even with G disconnected and limits closed, the fan relay on the board may be stuck, requiring board replacement.
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Repair Difficulty
Medium
3/5
Required Part
Integrated Furnace Control Board
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