BoilerFaultCodesGlow-worm F74 Fault Code
The Glow-worm F74 fault code means: your boiler has lost the ability to monitor its own water pressure, meaning it has shut down as a safety precaution.. It appears on 9 Glow-worm models in our database.
Technical description: Pressure sensor fault
What causes the Glow-worm F74 fault?
This fault occurs when the internal sensor responsible for monitoring water levels becomes blocked with debris or suffers an electrical failure. Over time, sludge in the heating system can coat the sensor's delicate diaphragm, preventing it from sending a clear signal to the main control board. Without this vital data, the boiler cannot confirm it has enough water to operate safely and will shut down to prevent 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 F74 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Glow-worm F74 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