BoilerFaultCodesGlow-worm F.29 Fault Code
Also written as F29 — same fault.
The Glow-worm F.29 fault code means: your boiler was lit but the flame has gone out unexpectedly, which has caused the system to stop working for safety.. It appears on 6 Glow-worm models in our database.
Technical description: Flame loss
What causes the Glow-worm F.29 fault?
This fault occurs when the boiler successfully ignites but cannot maintain the flame, leading the system to shut down for safety. The most common reasons include an inadequate gas supply, debris on the burner, or a faulty sensor that can no longer detect that the flame is actually lit.
This fault is more common during extreme cold snaps, as freezing temperatures can cause the external gas regulator to stick or the condensate pipe to freeze and back up.
DIY fix possible
Check that your gas emergency control valve is open and you have credit on your gas meterPress the 'Reset' button (indicated by a flame with a cross through it) for five secondsDuring freezing weather, check if your external white plastic condensate pipe has frozen and thaw it with warm water
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Gas Safe Register →Glow-worm models that show the F.29 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Glow-worm F.29 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