BoilerFaultCodesGlow-worm F7 Fault Code
The Glow-worm F7 fault code means: your boiler has detected a problem with the temperature sensor in its hot water storage tank, which means it may struggle to heat your water correctly.. It appears on 5 Glow-worm models in our database.
Technical description: Domestic hot water storage vessel thermistor fault
What causes the Glow-worm F7 fault?
This fault occurs when the sensor responsible for monitoring the temperature inside the boiler's internal hot water storage tank fails or sends an incorrect signal. The most common reason is that the sensor has developed an electrical fault due to age or internal wear, meaning the boiler can no longer tell how hot the water is. Occasionally, this can also be caused by loose or damaged wiring connecting the sensor to the main control board.
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 F7 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Glow-worm F7 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