BoilerFaultCodesGlow-worm Neon 4 lit (No) Fault Code
Also written as NEON4LITNO — same fault.
The Glow-worm Neon 4 lit (No) fault code means: your boiler is failing to light the gas flame or cannot detect that the flame has started, so it has shut down for safety.. It appears on 2 Glow-worm models in our database.
Technical description: Ignition, pilot or flame proving fault
What causes the Glow-worm Neon 4 lit (No) fault?
This fault occurs when the boiler tries to start but fails to either generate a spark or open the gas flow to create a flame. The most common reasons are a worn-out ignition electrode that can no longer create a spark or a faulty gas valve that isn't letting fuel into the burner.
DIY fix possible
Check if other gas appliances, like a cooker hob, are working to ensure gas is reaching the property.Verify that your gas pre-payment meter (if applicable) has credit.Turn the boiler selector switch to 'Reset' for 5 seconds, then back to the heater/hot water setting.
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 (No) fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Glow-worm Neon 4 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