High
5 flashes on Worcester Bosch Greenstar 25CDi

Your boiler has identified that the fan responsible for clearing exhaust fumes is not spinning at the correct speed, preventing it from starting safely.

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 speed too low. Check fan lead and connector, and fan; replace as necessary.

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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