Illuminated reset light High

Glow-worm Illuminated reset light Fault Code

Also written as ILLUMINATEDRESETLIGHT — same fault.

The Glow-worm Illuminated reset light fault code means: your boiler has switched itself off because it has reached an unsafe temperature and needs to be cooled down and reset.. 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: Safety Temperature Limiter (overheat) operates. Turn temperature control to '0' and then back to original position.

What causes the Glow-worm Illuminated reset light fault?

This fault occurs when the water inside the heat exchanger becomes too hot, triggering a safety switch to prevent damage. The most common reasons are a pump failure that stops water from moving around the system or a build-up of sludge that creates a blockage.

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

Typical repair cost £100-280 (including labour)

DIY fix possible

Check that your radiator valves are open and not turned to zero.Turn the boiler temperature control knob to the 'O' position.Wait a few minutes for the unit to cool, then turn the knob back to your desired temperature setting to reset the fault.

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Glow-worm models that show the Illuminated reset light fault code

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

Source

Glow-worm Illuminated reset light 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