F.XX High

Boiler Fault Code F.XX

Also written as FXX — same fault.

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed

Fault code F.XX appears across 3 boiler brands and 14 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 general internal error that is stopping it from working properly, and it now needs a professional diagnostic assessment to identify the specific cause. (As reported on Vaillant ecoTEC Plus 610)

Pick your boiler brand for the F.XX fix

Heatline F.XX 4 models Remeha F.XX 2 models Vaillant F.XX 8 models

Source

Information for the F.XX 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