205 Medium

Boiler Fault Code 205

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed

Fault code 205 appears across 3 boiler brands and 9 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.

Most common meaning Your boiler has lost the wireless or wired communication with its external temperature sensor, meaning it doesn't know how hard it needs to work to heat your home. (As reported on Ariston Alteas One)

Pick your boiler brand for the 205 fix

Ariston 205 1 model Navien 205 7 models Worcester Bosch 205 1 model

Source

Information for the 205 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