Thermeau
Post-Purge Fan Overrun
Heater fan continues to run for an unusually long time after burners shut off.
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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
Control board post-purge timer stuck, Flue temperature sensor reading high, Relay on Thermeau board welded closed, Wiring short keeping fan energized
How to Fix / Troubleshooting
Safety first: Turn off power before accessing the control board or fan wiring.
- Understand normal behavior: Some post-purge fan run is normal to cool the heat exchanger. Compare duration to Thermeau specifications.
- Check flue temperature: If the flue sensor reads high after shutdown, the board may keep the fan on. Investigate causes of high flue temperature such as scale or vent blockage.
- Inspect board relays: Look for signs of overheating or damage on the fan relay. A stuck relay can keep the fan running.
- Wiring check: Ensure the fan is wired only through the control board and not accidentally tied to constant power.
- Replace board if needed: If the relay is welded or logic is faulty, replace the Thermeau control board.
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Repair Difficulty
Medium
3/5
Required Part
Thermeau Main Control Board
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