BoilerFaultCodesGlow-worm F63 Fault Code
The Glow-worm F63 fault code means: your boiler's main internal computer has developed a communication failure, meaning it can no longer control the heating and hot water functions.. It appears on 9 Glow-worm models in our database.
Technical description: Main PCB fault
What causes the Glow-worm F63 fault?
This fault occurs when the boiler's main control board suffers an internal component failure or a memory error, preventing it from processing instructions. It is often caused by general electrical wear and tear over time or a sudden power surge that damages the delicate circuitry on the board. In some cases, loose or damaged wiring between the board and other internal components can also trigger this communication breakdown.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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Gas Safe Register →Glow-worm models that show the F63 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Glow-worm F63 fault code information on this page is sourced and cross-checked against the official Glow-worm service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026