BoilerFaultCodesGlow-worm Neon 2 lit (No) Fault Code
Also written as NEON2LITNO — same fault.
The Glow-worm Neon 2 lit (No) fault code means: your boiler has become too hot and has automatically shut down for safety purposes.. It appears on 2 Glow-worm models in our database.
Technical description: Overheat cut off device tripped or thermostat, overheat cut off device faulty
What causes the Glow-worm Neon 2 lit (No) fault?
This fault occurs when the water inside your boiler reaches an unsafe temperature, triggering a safety switch to cut the power. It is often caused by a failing pump that can no longer move heat away from the boiler quickly enough or a buildup of limescale and sludge that restricts water flow. In some cases, the safety sensor itself may have developed a fault and is wrongly reporting that the unit is overheating.
This issue often surfaces when you first turn your heating back on in autumn, as circulation pumps can seize up after being idle throughout the summer.
DIY fix possible
Ensure all radiator valves are fully open to allow water flowLocate the reset button or switch on the boiler control panelPress the reset button once; if the light returns immediately, do not attempt further resets
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Gas Safe Register →Glow-worm models that show the Neon 2 lit (No) fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Glow-worm Neon 2 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