Boiler Fault Code 365 / Fb

Also written as 365FB — same fault.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026

Fault code 365 / Fb appears across 1 boiler brand and 2 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 a potential issue with its internal gas supply system during its safety self-check, meaning it will remain locked out to prevent unsafe operation. (As reported on Worcester Bosch Greenstar CDi Compact)