High Lockout
C6 on Worcester Bosch Greenstar CDi Compact

Your boiler has detected that the internal fan is spinning too fast, causing the system to shut down 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

Fan problem - Fan running too fast or too slow

What causes this fault?

This fault occurs when the boiler's control system loses the ability to regulate the fan speed, causing it to run faster than safety limits allow. The most common reason is a communication failure between the fan motor and the main circuit board, often due to worn-out bearings or a fault on the board's control module.

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 →C7View →

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