BoilerFaultCodes ALL 98 High
Boiler Fault Code ALL 98
Also written as ALL98 — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code ALL 98 appears across 1 boiler brand and 3 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 is having trouble starting up correctly, which means it cannot operate your heating or hot water safely. (As reported on Sime Brava Slim HE Regular)
Pick your boiler brand for the ALL 98 fix
Source
Information for the ALL 98 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 7 July 2026