BoilerFaultCodesGlow-worm Neon 4 NOT lit Fault Code
Also written as NEON4NOTLIT — same fault.
The Glow-worm Neon 4 NOT lit fault code means: your boiler has failed to light the pilot flame or cannot verify that the burner is safely lit, resulting in no heating or hot water.. It appears on 3 Glow-worm models in our database.
Technical description: Ignition, pilot or flame proving fault.
What causes the Glow-worm Neon 4 NOT lit fault?
This fault occurs when the boiler tries to start but fails to establish or maintain the small pilot flame needed to light the main burner. The most common reasons are a blocked pilot hole preventing gas flow or a worn-out sensor that can no longer detect the heat from the flame. Without confirmation that it is safe to stay lit, the boiler shuts down as a safety precaution.
This issue often appears in autumn when the boiler is first switched back on after a long summer break, as debris or dust can settle in the pilot assembly during periods of inactivity.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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Glow-worm models that show the Neon 4 NOT lit fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Glow-worm Neon 4 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