BoilerFaultCodesGlow-worm 0 8 Fault Code
Also written as 08 — same fault.
The Glow-worm 0 8 fault code means: your boiler is failing to start because it cannot confirm that the internal fan is effectively clearing exhaust gases, which prevents it from igniting safely.. It appears on 1 Glow-worm model in our database.
Technical description: The Air pressure switch has not closed.
What causes the Glow-worm 0 8 fault?
This fault occurs when the boiler's internal drainage system becomes backed up with liquid that can no longer escape. The most common reason is a blockage in the external pipe, often caused by a buildup of sludge or debris within the condensate trap itself. When the water level rises too high inside the unit, a safety sensor shuts the system down to prevent internal leaking or damage.
This fault is significantly more common during freezing winter weather, as the external drainage pipe can ice up and prevent water from leaving the boiler.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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Glow-worm models that show the 0 8 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Glow-worm 0 8 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 7 July 2026