BoilerFaultCodesGlow-worm 13 Fault Code
The Glow-worm 13 fault code means: your boiler's internal computer has developed a fault and can no longer control the heating system safely.. It appears on 8 Glow-worm models in our database.
Technical description: Main board fault
What causes the Glow-worm 13 fault?
This fault occurs when the boiler's central control unit suffers an internal electrical failure or memory error. It is typically caused by ageing capacitors on the circuit board or sudden electrical surges that damage the delicate microprocessors. Because the 'brain' of the boiler can no longer communicate with the sensors and gas valve, the unit shuts down to prevent unsafe operation.
This fault is slightly more common during winter months when the boiler is working under high demand or following heavy thunderstorms which can cause electrical spikes in the local grid.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Glow-worm models that show the 13 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Glow-worm 13 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