BoilerFaultCodesGlow-worm 41 Fault Code
The Glow-worm 41 fault code means: your boiler's internal computer has developed a fault and can no longer communicate with the rest of the system safely.. It appears on 1 Glow-worm model in our database.
Technical description: There is an internal fault in the Automatic Control Module.
What causes the Glow-worm 41 fault?
This fault occurs when the boiler's main control board experiences an internal electronic failure or a breakdown in its memory processing. It is usually caused by aging electrical components on the circuit board that have finally worn out or been damaged by a sudden power surge. Because the 'brain' of the boiler can no longer verify that it is operating safely, it shut downs the system entirely to prevent any hazards.
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 41 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Glow-worm 41 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