BoilerFaultCodesGlow-worm F.74 Fault Code
Also written as F74 — same fault.
The Glow-worm F.74 fault code means: your boiler's internal sensor that monitors water pressure has experienced an electrical failure and can no longer tell if there is enough surface water for the system to run safely.. It appears on 6 Glow-worm models in our database.
Technical description: Electrical problem in the water pressure sensor
What causes the Glow-worm F.74 fault?
This fault occurs when the boiler's internal computer loses communication with the water pressure sensor, often due to an electrical short or a component failure inside the sensor itself. Without a reliable reading, the boiler cannot confirm there is enough water to operate safely and will shut down to prevent internal damage. The most common reason is general wear and tear of the sensor's electronics, though a loose connection in the wiring can also trigger the error.
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.74 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Glow-worm F.74 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