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 is not receiving electrical power or has an internal blown fuse, meaning it cannot start the ignition process.. It appears on 7 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 required to wake up the boiler is broken, preventing the control board from receiving power. The most common reason is a blown fuse within the boiler or at the wall switch, often caused by a sudden electrical surge or a faulty internal component like a failing pump or fan. If the fuses are intact, it typically indicates that the main printed circuit board has suffered an electrical failure and can no longer process commands.
DIY fix possible
Check if your home's main electrical consumer unit has a tripped circuit breakerEnsure the boiler's external switch or fused spur is turned onChange the fuse (usually 3A) in the external wall switch/spur
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Gas Safe Register →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 27 April 2026