BoilerFaultCodes AL 56 High
Boiler Fault Code AL 56
Also written as AL56 — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code AL 56 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 shut down because the temperature difference between the water going out and the water coming back is too high, suggesting the water isn't circulating properly. (As reported on Sime Dewy 30/130 HE FS)
Pick your boiler brand for the AL 56 fix
Source
Information for the AL 56 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