BoilerFaultCodesGlow-worm Neon 4 lit Fault Code
Also written as NEON4LIT — same fault.
The Glow-worm Neon 4 lit fault code means: your boiler is failing to light the small internal flame needed to start the main burner, which means your heating and hot water will not work.. It appears on 2 Glow-worm models in our database.
Technical description: Is there a spark at pilot burner? Check lead continuity and inspect electrode and lead for damage.
What causes the Glow-worm Neon 4 lit fault?
This fault occurs when the boiler's ignition system fails to create the small pilot flame required to safely light the main burner. The most common reasons are a worn-out spark electrode that can no longer produce a spark, or a tiny blockage in the pilot injector preventing gas from reaching the ignition point.
This issue often surfaces during the first cold spell of autumn when a boiler that has been idle over summer is suddenly asked to work hard, causing aging ignition components to finally fail.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Glow-worm models that show the Neon 4 lit fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Glow-worm Neon 4 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