F12 Medium

Boiler Fault Code F12

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed

Fault code F12 appears across 6 boiler brands and 18 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 its connection to the sensor that monitors your hot water temperature, which means you will likely experience cold showers until it is fixed. (As reported on Ferroli Modena HE)

Pick your boiler brand for the F12 fix

Euroterm F12 1 model Ferroli F12 10 models Glow-worm F12 2 models Ideal F12 1 model Saunier Duval F12 2 models Vaillant F12 2 models

Source

Information for the F12 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