BoilerFaultCodes 0.99 High
Boiler Fault Code 0.99
Also written as 099 — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code 0.99 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 has detected a communication error between its internal electronic control systems, preventing it from operating correctly. (As reported on Johnson Starley Aquair S 10)
Pick your boiler brand for the 0.99 fix
Source
Information for the 0.99 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