BoilerFaultCodesGlow-worm Red light Fault Code
Also written as REDLIGHT — same fault.
The Glow-worm Red light fault code means: your boiler has shut down for safety because it cannot maintain a steady pilot light or has detected a problem with how waste gases are being removed.. It appears on 2 Glow-worm models in our database.
Technical description: Indicates that the pilot light is not operating correctly, or the combustion products discharge safety device has been activated (lockout).
What causes the Glow-worm Red light fault?
This fault occurs when the boiler's internal sensors detect that the pilot flame has gone out or that dangerous exhaust gases are not leaving the flue correctly. The most common reason is a worn-out sensor failing to detect the flame, though it can also be triggered if a blockage in the chimney or wind gust disrupts the burner.
This issue often appears during the first cold snap of autumn when the boiler is pushed to run for longer periods after being idle all summer.
DIY fix possible
Check if other gas appliances (like a cooker) are working to confirm gas supplyLocate the reset button (usually a small button or dial on the front panel)Press and hold the reset button for several seconds to try and reignite the pilot light
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Gas Safe Register →Glow-worm models that show the Red light fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Glow-worm Red 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