Medium
237 on Worcester Bosch Greenstar CDi Compact

Your boiler's fan is running constantly even when it should be off, which usually indicates that the system is trying to clear out internal air or has detected a sensor error.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Book a service

This fault should be looked at by a Gas Safe engineer within the next week or two. It may get worse if left.

What the manual says

Manufacturer manual

C4 Airflow present during last 24 hours - fan running continuously

From this model's manual
Verified against the Worcester Bosch Greenstar Cdi Compact installation & service manual, page 65.
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 fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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