BoilerFaultCodesGlow-worm F.73 Fault Code
Also written as F73 — same fault.
The Glow-worm F.73 fault code means: your boiler has lost signal from its internal water pressure monitor, meaning it cannot confirm if there is enough water to run safely.. It appears on 6 Glow-worm models in our database.
Technical description: Water pressure sensor not connected or has short-circuited
What causes the Glow-worm F.73 fault?
This fault occurs when the boiler's main control board loses electrical communication with the water pressure sensor. The most common reason is a loose or damaged connection in the internal wiring, or the sensor itself has developed an electrical fault and failed. Without this signal, the boiler shuts down as a safety precaution because it cannot confirm there is enough water to operate without 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 F.73 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Glow-worm F.73 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