High
12 on Worcester Bosch Greenstar CDi Compact

Your boiler has detected an issue with the internal fan that pushes exhaust gases out, meaning it has safely shut itself down to prevent unsafe operation.

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.

What the manual says

Manufacturer manual

Locking Fan running too fast Defective fan or blocked air way. Fan running too slow No airflow after defined period of time Fan not running

From this model's manual
Verified against the Worcester Bosch Greenstar Cdi Compact installation & service manual.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

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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