High Lockout
F.74 on Glow-worm Energy Heat

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.

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description

Electrical problem in the water pressure sensor

What causes this 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 is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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