BoilerFaultCodesGlow-worm Neon 1 lit (No) Fault Code
Also written as NEON1LITNO — same fault.
The Glow-worm Neon 1 lit (No) fault code means: your boiler has lost electrical power, which is usually caused by an issue with the mains supply or a blown internal fuse.. It appears on 2 Glow-worm models in our database.
Technical description: Fault with mains supply or PCB fuse
What causes the Glow-worm Neon 1 lit (No) fault?
This fault occurs when the boiler is not receiving the electrical power it needs to operate, causing the control panel to go dark except for the error light. The most common reason is a blown fuse on the main circuit board or a tripped switch in your home's fuse box, often triggered by a sudden power surge or a failing internal component. In some cases, it can simply be that the external power switch for the boiler has been accidentally turned off.
This fault is slightly more common during the winter months when power grids are under higher load or during stormy weather, as electrical surges and lightning strikes are more likely to blow sensitive internal fuses.
DIY fix possible
Check if other appliances in the house are working to rule out a general power cutEnsure the boiler's fused spur switch (usually near the boiler) is turned onCheck your home's main consumer unit (fuse box) to see if a circuit breaker has tripped
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Gas Safe Register →Glow-worm models that show the Neon 1 lit (No) fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Glow-worm Neon 1 lit (No) 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