F13 error, furnace shuts down with signs of overheating in flue area

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.

Possible Causes

Faulty flue gas temperature sensor, Blocked or restricted flue on Glow-worm furnace, Incorrect burner setting causing high flue temperature, Heat exchanger partially blocked

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 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.

Repair Difficulty

Professional Required 5/5

Required Part

Flue Gas Temperature Sensor

Check Price on Amazon

We may earn a commission from links on this page.