BoilerFaultCodes ALL 04 Medium
Boiler Fault Code ALL 04
Also written as ALL04 — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code ALL 04 appears across 1 boiler brand and 7 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 communication problem with the part that monitors the temperature of your hot water, which may cause your hot water to stop working or not reach the correct temperature. (As reported on Sime Murelle HE System)
Pick your boiler brand for the ALL 04 fix
Source
Information for the ALL 04 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