Thermo Pride
Fan Control or Limit Sensor Drift
Furnace blower starts and stops repeatedly without any heat call (fan cycling by itself).
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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
Faulty fan limit switch on older Thermo Pride models, Temperature sensor drift on control board, Residual heat triggering fan, Shorted fan control wiring
How to Fix / Troubleshooting
Safety First: Turn off power before accessing fan/limit controls.
- Check for residual heat: After a long heat cycle, some fan cycling is normal as the heat exchanger cools. Persistent cycling is not.
- Inspect fan/limit control (if equipped): On older models with a mechanical fan/limit, ensure the dial moves freely and settings match the Thermo Pride manual.
- Control board sensor: If the board misreads temperature, it may cycle the fan. Board replacement may be required.
- Professional diagnosis: Have a technician verify temperature readings and fan control operation.
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Repair Difficulty
Medium
3/5
Required Part
Fan Limit Switch
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