b35 High

Boiler Fault Code b35

Also written as B35 — same fault.

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed

Fault code b35 appears across 1 boiler brand and 1 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.

Most common meaning Your boiler's computer parts are having trouble talking to each other, which prevents the system from starting up. (As reported on Johnson Starley Warmcair DW)

Pick your boiler brand for the b35 fix

Johnson Starley b35 1 model

Source

Information for the b35 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