BoilerFaultCodes AL 84 High
Boiler Fault Code AL 84
Also written as AL84 — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code AL 84 appears across 1 boiler brand and 6 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.
Most common meaning Your boiler is not receiving enough gas to operate correctly, which is likely caused by an issue with your external gas supply or a blockage in the pipework. (As reported on Sime Dewy 30/50 HE WM)
Pick your boiler brand for the AL 84 fix
Source
Information for the AL 84 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