F3
FAULT CODE
Glow-worm
Flue Gas Sensor Fault
High Severity
Engineer Required
The flue gas temperature sensor is reading outside normal range.
Step-by-Step Fix Guide
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Step 1
Check external flue for blockages
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Step 2 Engineer only
A Gas Safe engineer should test the flue gas sensor
Gas Safe Reminder
Work on gas appliances must be carried out by a Gas Safe registered engineer. The steps above cover safe checks a homeowner can perform - any internal component replacement requires a qualified professional. If in doubt, always call an engineer.