Sime
Fan Stuck On
Furnace fan runs continuously even when there is no call for heat.
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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
Stuck fan relay on control board, Faulty fan run‑on timer, Incorrect thermostat wiring, Overheat condition not resetting
How to Fix / Troubleshooting
Safety first: Turn off power before accessing the control board.
- Check thermostat wiring: Ensure there are no unintended links causing a constant fan command.
- Allow unit to cool: If the fan is in overrun mode due to recent overheating, it should stop after the programmed time. If not, proceed with checks.
- Inspect control board: Look for signs of burnt or stuck relays. Tapping lightly may temporarily release a stuck relay, confirming the fault.
- Replace control board if needed: A technician should replace the board if the fan relay is defective.
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Repair Difficulty
Medium
3/5
Required Part
Main Control Board
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