Medium Warning
5.b on Worcester Bosch Greenstar CDi Compact

Your boiler's fan is running longer than it should after the heating has turned off, which is usually a sign of a communication error between internal components.

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.

Technical description

Fan over-run time

What causes this fault?

This fault occurs when the boiler's internal computer stays in a cooling phase for too long because it can no longer accurately track the fan's speed. The most common reason is a communication breakdown where the control board receives incorrect signals from the fan, causing the system to keep the fan running as a safety precaution. Over time, heat stress or moisture can degrade the electrical connections or the sensitive circuitry within the fan motor itself.

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Related fault codes

C1View →C6View →

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