High
S9 on Worcester Bosch Highflow 550 CDi

Your boiler has detected that a safety link or internal connector has become loose or disconnected, causing it to stop operating to prevent damage.

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

Terminals ST15 not bridged at connection ST8

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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