BoilerFaultCodesGlow-worm 28 Fault Code
The Glow-worm 28 fault code means: your boiler has stopped working because the internal fan, which safely exhausts fumes, is not spinning correctly or communicating with the system.. It appears on 1 Glow-worm model in our database.
Technical description: The fan is stationary or there is no fan speed signal.
What causes the Glow-worm 28 fault?
This fault occurs when the boiler's control system detects that the fan is either not spinning at all or is spinning at the wrong speed to safely expel exhaust gases. The most common reason is a mechanical failure within the fan motor itself, though a loose electrical connection or a fault on the main control board can also stop the fan from receiving power.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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Gas Safe Register →Glow-worm models that show the 28 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Glow-worm 28 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