F13
Glow-worm
Flue Gas Temperature Overheat
F13 error: The furnace shuts down with signs of overheating in the flue area.
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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 flue gas temperature sensor, Blocked or restricted flue on the Glow-worm furnace, Incorrect burner setting causing high flue temperature, Partially blocked heat exchanger
How to Fix / Troubleshooting
Safety: Risk of flue gas spillage and CO. Isolate the appliance and do not operate until checked by a qualified engineer.
Technician steps:
- Inspect the flue gas temperature sensor and its wiring. Test sensor resistance and replace if out of range.
- Check the flue system for blockages, incorrect slope, or damage.
- Inspect the primary heat exchanger for signs of blockage or poor heat transfer.
- Perform a combustion analysis and adjust burner settings within Glow-worm limits.
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Repair Difficulty
Professional Required
5/5
Required Part
Flue Gas Temperature Sensor
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