High Lockout
9.b on Worcester Bosch Greenstar CDi Compact

Your boiler's fan is not spinning at the correct speed, which prevents the system from safely starting the combustion process.

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

Actual fan speed (Hz)

What causes this fault?

This fault occurs when the boiler's internal computer is unable to confirm that the fan is spinning at the required speed to safely clear waste gases. It is usually caused by a physical failure of the fan motor, a loose connection in the wiring, or a fault on the main control board that prevents it from reading the fan's speed correctly.

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

C1View →C6View →9AView →

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