BoilerFaultCodesGlow-worm 18 Fault Code
The Glow-worm 18 fault code means: your boiler's control panel and its main computer are having trouble communicating with each other, meaning you cannot change settings or see the boiler's status correctly.. It appears on 4 Glow-worm models in our database.
Technical description: Local user interface fault
What causes the Glow-worm 18 fault?
This fault occurs when the data connection between the front display screen and the boiler's internal computer is interrupted or fails. The most common reason is a loose internal wire or a component failure on one of the circuit boards caused by general wear and tear over time. Because the 'brain' of the boiler can no longer talk to the control panel, the unit stops operating for safety.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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Search the official register for a qualified engineer in your area.
Gas Safe Register →Glow-worm models that show the 18 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Glow-worm 18 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