BoilerFaultCodesGlow-worm Reset light (illuminated) Fault Code
Also written as RESETLIGHTILLUMINATED — same fault.
The Glow-worm Reset light (illuminated) fault code means: your boiler has become too hot and has automatically shut down to protect itself, usually because the water inside isn't circulating properly.. It appears on 4 Glow-worm models in our database.
Technical description: Overheat safety cutoff device may need resetting
What causes the Glow-worm Reset light (illuminated) fault?
This fault occurs when the water inside the heat exchanger reaches a dangerously high temperature, triggering a safety switch to cut off the burner. The most common reason is a failure in the circulation pump or a blockage in the pipes, which prevents the heat from being carried away to your radiators. It can also be caused by air trapped in the system or a faulty sensor incorrectly reading the temperature.
This issue often surfaces at the start of autumn when the heating is turned back on after a long summer break, as pump components can seize up during periods of inactivity.
DIY fix possible
Ensure all radiator valves are fully open to allow water flow.Check that the system pressure is at the correct level (usually 1.0 to 1.5 bar).Press the reset button or turn the control knob to 'Off/Reset' and then back to 'On' to restart the boiler.
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Gas Safe Register →Glow-worm models that show the Reset light (illuminated) fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Glow-worm Reset light (illuminated) 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