BoilerFaultCodesGlow-worm 01 Fault Code
The Glow-worm 01 fault code means: your boiler has stopped working because it cannot light the gas burner to provide heating or hot water, usually because the gas supply is interrupted or the ignition spark has failed.. It appears on 3 Glow-worm models in our database.
Technical description: Ignition fault (lockout) caused by no gas, no detection
What causes the Glow-worm 01 fault?
This fault occurs when the boiler attempts to light but fails to detect a flame after several tries, forcing the system into a safety shutdown. The most common reasons are an interruption in the gas supply, a build-up of carbon on the ignition probes, or a component failure that prevents the spark from starting the fire.
This fault is more common during the first cold snap of winter, as gas valves can occasionally stick after long periods of inactivity during the summer.
DIY fix possible
Check if your gas meter has credit or if other gas appliances in your home are working.Ensure the blue gas isolation valve under the boiler is in the 'open' position (aligned with the pipe).Press the 'Reset' button (indicated by a flame with a line through it) and hold for one second.
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Gas Safe Register →Glow-worm models that show the 01 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Glow-worm 01 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