BoilerFaultCodes S9 High
Boiler Fault Code S9
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code S9 appears across 1 boiler brand and 4 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.
Most common meaning Your boiler has detected that a safety link or internal connector has become loose or disconnected, causing it to stop operating to prevent damage. (As reported on Worcester Bosch Highflow 550 CDi)
Pick your boiler brand for the S9 fix
Source
Information for the S9 fault code is sourced from the official service / installation manual for each model that displays it. Read more about how we source fault codes →
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026