High Lockout
73 on Worcester Bosch Greenstar Utility 18/25

Your boiler's internal pump or motor is not receiving power or has stopped working, meaning it cannot circulate heat through your system.

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

Faulty motor or electrical supply to motor

What causes this fault?

This fault occurs when the boiler's internal pump fails to move water, which prevents heat from leaving the unit and reaching your radiators. The most common reasons are a physical blockage or mechanical failure within the pump motor itself, or a communication issue where the main control board is unable to send electricity to the pump.

This fault is frequently seen at the start of autumn when systems are turned back on after sitting idle all summer, which can cause the pump internal parts to seize up.

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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Related fault codes

72View →C1View →C6View →

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