BoilerFaultCodesGlow-worm Indicator 1 (Reset) Lit Fault Code
Also written as INDICATOR1RESETLIT — same fault.
The Glow-worm Indicator 1 (Reset) Lit fault code means: your boiler has switched itself off as a safety precaution because it has either detected a fault or has become too hot.. It appears on 3 Glow-worm models in our database.
Technical description: Non - Volatile Lockout / Reset O/H or in 'standby' mode
What causes the Glow-worm Indicator 1 (Reset) Lit fault?
This fault occurs when the internal safety sensors detect that the water inside the unit has reached a dangerously high temperature or if the system has failed to ignite properly. The most common reason is a lack of water circulation, often caused by a failing pump or a blockage in the pipework that prevents heat from moving away from the boiler. It can also be triggered by a faulty control board incorrectly reading the system's temperature.
This issue often appears when the heating is first turned on in autumn, as pump components can seize up after being inactive during the summer months.
DIY fix possible
Locate the reset button on the control panel.Press and release the reset button to see if the boiler restarts.Check that your heating controls (thermostat) are calling for heat.Ensure your gas supply is active and hasn't been interrupted.
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Gas Safe Register →Glow-worm models that show the Indicator 1 (Reset) Lit fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Glow-worm Indicator 1 (Reset) 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