BoilerFaultCodesGlow-worm F00 Fault Code
The Glow-worm F00 fault code means: your boiler has stopped working because it cannot correctly measure the temperature of the water leaving the unit.. It appears on 9 Glow-worm models in our database.
Technical description: Flow heating thermistor fault
What causes the Glow-worm F00 fault?
This fault occurs when the boiler's main control board loses communication with the sensor that monitors the temperature of the water sent to your radiators. The most common reason is that the sensor itself has suffered an internal electrical failure, or the wiring connecting it to the brain of the boiler has become loose or damaged. Without this data, the boiler shuts down as a safety precaution to prevent the system from overheating.
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 F00 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Glow-worm F00 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