78 High

Boiler Fault Code 78

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed

Fault code 78 appears across 8 boiler brands and 28 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 temporary internal communication error or a sensor synchronization issue that is preventing it from running properly. (As reported on Vokera Easi-Heat I)

Pick your boiler brand for the 78 fix

Alpha 78 4 models Atag 78 9 models Biasi 78 4 models ECA 78 1 model Ideal 78 5 models Keston 78 2 models Vokera 78 2 models Worcester Bosch 78 1 model

Source

Information for the 78 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 31 August 2026