BoilerFaultCodesGlow-worm F73 Fault Code
The Glow-worm F73 fault code means: your boiler is struggling to read its own water level because of an electrical sensor issue, which has caused it to stop working as a safety precaution.. It appears on 9 Glow-worm models in our database.
Technical description: Water pressure sensor fault
What causes the Glow-worm F73 fault?
This fault occurs when the boiler's internal computer loses communication with the sensor that monitors water pressure. The most common reason is that the sensor has developed an electrical internal short or the wiring connecting it to the main control board has become loose or damaged. Without an accurate pressure reading, the boiler shuts down to prevent itself from firing while potentially dry.
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 F73 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Glow-worm F73 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