BoilerFaultCodesGlow-worm F.64 Fault Code
Also written as F64 — same fault.
The Glow-worm F.64 fault code means: your boiler's internal computer is having trouble processing electrical signals from its various sensors.. It appears on 6 Glow-worm models in our database.
Technical description: Electronics/sensor/analogue-to-digital converter fault
What causes the Glow-worm F.64 fault?
This fault occurs when the boiler's main control board fails to correctly interpret the electrical signals coming from its internal sensors. It is usually caused by a critical electronic failure within the circuit board itself or a short circuit in the wiring that confuses the boiler's computer. In some cases, a faulty temperature sensor can send an erratic voltage that the system can no longer process safely.
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 F.64 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Glow-worm F.64 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