BoilerFaultCodesGlow-worm Red lockout neon (lit) Fault Code
Also written as REDLOCKOUTNEONLIT — same fault.
The Glow-worm Red lockout neon (lit) fault code means: your boiler has shut itself down for safety because it either got too hot or failed to light the gas properly.. It appears on 1 Glow-worm model in our database.
Technical description: Boiler has entered lockout mode. Can be caused by the overheat cut-off going open circuit or failure to detect flame.
What causes the Glow-worm Red lockout neon (lit) fault?
This fault occurs when the boiler's internal safety sensors detect that the unit has become dangerously hot or that the gas has failed to ignite after several attempts. The most common reasons are a lack of water circulation causing the heat exchanger to trap too much heat, or worn-out ignition parts that can no longer create a spark to light the burner.
This issue is more frequent during the first cold snap of autumn when pumps that have been idle all summer often seize up, leading to immediate overheating.
DIY fix possible
Locate the reset button (often marked with a flame symbol or 'R') on the control panelPress and hold the reset button for several seconds and wait for the boiler to restartCheck that your gas pre-pay meter has credit and that other gas appliances like your hob are working
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Gas Safe Register →Glow-worm models that show the Red lockout neon (lit) fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Glow-worm Red lockout neon (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