BoilerFaultCodesGlow-worm 10 Fault Code
The Glow-worm 10 fault code means: your boiler has stopped working because a sensor that monitors the temperature of the water returning from your radiators has developed a fault.. It appears on 4 Glow-worm models in our database.
Technical description: Central heating return NTC fault
What causes the Glow-worm 10 fault?
This fault occurs when the sensor responsible for measuring the temperature of the water returning to the boiler begins sending incorrect data or stops communicating entirely. The most common reason is that the internal components of the sensor have degraded over time or the electrical connection has become loose or damaged. Because the boiler can no longer accurately monitor the system temperature, it shuts down as a safety precaution to prevent overheating.
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 10 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Glow-worm 10 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