BoilerFaultCodesGlow-worm Neon 1 NOT lit Fault Code
Also written as NEON1NOTLIT — same fault.
The Glow-worm Neon 1 NOT lit fault code means: your boiler appears to have no power reaching it, which is likely caused by an external electrical issue or a blown fuse inside the unit.. It appears on 3 Glow-worm models in our database.
Technical description: Fault with mains supply or PCB fuse.
What causes the Glow-worm Neon 1 NOT lit fault?
This fault occurs when the electrical circuit feeding the boiler is broken, meaning the unit cannot receive the power it needs to operate. The most common reason is a blown fuse within the boiler's internal control board or an issue with the external power switch on the wall. In some cases, a power surge or a failing internal component can cause the fuse to pop as a safety precaution to protect the sensitive electronics.
DIY fix possible
Check if your home's main fuse board (consumer unit) has tripped and flip the switch back if necessary.Locate the fused spur switch near the boiler (usually a wall switch with a red light) and ensure it is turned on.Check if other appliances in the house are working to rule out a general power cut.
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Glow-worm models that show the Neon 1 NOT lit fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Glow-worm Neon 1 NOT lit 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 31 August 2026