BoilerFaultCodes 3 06 High
Boiler Fault Code 3 06
Also written as 306 — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code 3 06 appears across 2 boiler brands and 22 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.
Most common meaning Your boiler's internal computer is experiencing a communication error and cannot operate safely, meaning your heating and hot water will be unavailable. (As reported on Ariston Clas ONE R)
Pick your boiler brand for the 3 06 fix
Source
Information for the 3 06 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