Reset LED is lit High

Glow-worm Reset LED is lit Fault Code

Also written as RESETLEDISLIT — same fault.

The Glow-worm Reset LED is lit fault code means: your boiler has sensed it is getting too hot and has shut itself down as a safety precaution.. It appears on 4 Glow-worm models in our database.

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description: Check water system for overheating. Reset by turning temperature control knob off and on.

What causes the Glow-worm Reset LED is lit fault?

This fault occurs when the water inside the heat exchanger reaches a dangerously high temperature, triggering a safety sensor to cut the power. The most common reasons are a failed pump that isn't moving the water away fast enough, or a blockage such as air or sludge trapped within the pipework.

This issue often appears when the heating is first turned on after summer, as pump components can seize up during long periods of inactivity.

Typical repair cost £100-280 (including labour)

DIY fix possible

Check that all radiator valves are open and not turned to zero.Ensure there are no blockages in the system and that the pump is running.Reset the boiler by turning the temperature control knob to 'Off' and then back to your desired setting.

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Glow-worm models that show the Reset LED is lit fault code

Click a model for the full fault code list and model-specific repair notes.

Source

Glow-worm Reset LED is 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