BoilerFaultCodesGlow-worm F.00 Fault Code
Also written as F00 — same fault.
The Glow-worm F.00 fault code means: your boiler has stopped working because it cannot accurately measure the temperature of the water leaving the unit to heat your home.. It appears on 6 Glow-worm models in our database.
Technical description: Flow temperature sensor
What causes the Glow-worm F.00 fault?
This fault occurs when the boiler's main control board loses communication with the sensor that monitors the temperature of the water heading to your radiators. The most common reason is that the internal sensor has developed a physical defect or the electrical wiring connecting it to the brain of the boiler has become loose or damaged.
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 F.00 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Glow-worm F.00 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