High Lockout
F09 on Glow-worm Ci Plus

Your boiler has lost track of the system's water pressure because the internal sensor is either faulty or disconnected, causing the heating to stop working for safety.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

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

Water pressure sensor fault

What causes this fault?

This fault occurs when the boiler's internal computer can no longer detect the water pressure inside the system. The most common reason is that the pressure sensor has developed an internal electrical failure or has become blocked with debris, preventing it from sending a signal. In some cases, the thin wires connecting the sensor to the main control board may have come loose or suffered damage.

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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