BoilerFaultCodes ALL 23 Medium
Boiler Fault Code ALL 23
Also written as ALL23 — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code ALL 23 appears across 1 boiler brand and 3 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.
Most common meaning Your boiler is having trouble communicating with the secondary heating zone in your home, which means that specific area may not be receiving heat as expected. (As reported on Sime Murelle Elite HE 35T System)
Pick your boiler brand for the ALL 23 fix
Source
Information for the ALL 23 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