BoilerFaultCodesGlow-worm Neon 2 lit Fault Code
Also written as NEON2LIT — same fault.
The Glow-worm Neon 2 lit fault code means: your boiler has detected that the water pressure is too low to operate safely, causing it to lock out.. It appears on 2 Glow-worm models in our database.
Technical description: Is there 230V~ between K1 and N? Check 0.2 Bar of water pressure is available at boiler. If ok, Replace water pressure switch.
What causes the Glow-worm Neon 2 lit fault?
This fault occurs when the internal sensors detect that there isn't enough water pressure inside the system to safely heat your home. The most common reason is a slow leak in the pipework or radiators, though it can also happen if the system was recently drained and not refilled correctly. Without sufficient water, the boiler shuts down to prevent the internal components from overheating and sustaining permanent damage.
This issue often appears in autumn when homeowners turn their heating back on for the first time, as the system may have lost pressure gradually over the summer months.
DIY fix possible
Check the water pressure gauge on your system.If the pressure is below 1.0 bar, use the external filling loop to top up the system to 1.5 bar.Reset the boiler to see if the light clears.
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Gas Safe Register →Glow-worm models that show the Neon 2 lit fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Glow-worm Neon 2 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