BoilerFaultCodesGlow-worm 08 Fault Code
The Glow-worm 08 fault code means: your boiler has lost its ability to monitor the temperature of the stored hot water, meaning it cannot heat your water reliably or safely.. It appears on 5 Glow-worm models in our database.
Technical description: Storage vessel thermistor/wiring fault
What causes the Glow-worm 08 fault?
This fault occurs when the sensor responsible for monitoring the temperature inside the boiler's internal hot water storage tank fails or loses its connection. The most common reason is that the sensor has physically degraded over time or the electrical wiring has become loose or corroded, preventing the control board from knowing if the water is hot or cold.
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 08 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Glow-worm 08 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