FA High

Boiler Fault Code FA

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed

Fault code FA appears across 3 boiler brands and 64 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 that the temperature sensors for the water going in and out are reporting incorrect or swapped readings, which has caused the system to shut down for safety. (As reported on Ideal Logic Code Combi ESP1)

Pick your boiler brand for the FA fix

Ideal FA 14 models Viessmann FA 9 models Worcester Bosch FA 41 models

Source

Information for the FA 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