Cointra
Fan Stuck On / Post-purge Overrun
Furnace continues to blow cool air after the burner has shut off and does not stop.
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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 limit control, Incorrect fan off delay setting, Shorted thermostat wiring
How to Fix / Troubleshooting
Safety: Turn off power before accessing the control board.
Steps:
- Allow normal post-purge: Many Cointra furnaces run the fan for several minutes after burner shutdown. This is normal. If it runs indefinitely, continue.
- Check thermostat wiring: Ensure there are no shorts between fan and heat call terminals at the thermostat or furnace.
- Inspect fan limit control: If equipped with a mechanical fan limit, verify that the dial and pointers are correctly set and not stuck.
Professional service: A technician may need to replace a stuck relay or the main control board.
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Repair Difficulty
Medium
3/5
Required Part
Fan Limit Control
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