BoilerFaultCodesGlow-worm F64 Fault Code
The Glow-worm F64 fault code means: your boiler's main internal computer has developed a communication or hardware error and cannot manage the heating process safely.. It appears on 9 Glow-worm models in our database.
Technical description: Main PCB fault
What causes the Glow-worm F64 fault?
This fault occurs when the boiler's central control board suffers an internal hardware failure or loses the ability to communicate with its sensors. The most common reason is age-related wear on the electronic components or a sudden electrical surge that has damaged the delicate circuitry.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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Search the official register for a qualified engineer in your area.
Gas Safe Register →Glow-worm models that show the F64 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Glow-worm F64 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