High Lockout
F74 on Glow-worm Flexicom hx

Your boiler has lost the ability to monitor its own water pressure, meaning it has shut down as a safety precaution.

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

Pressure sensor fault

What causes this 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 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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