BoilerFaultCodes AL40 High
Boiler Fault Code AL40
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code AL40 appears across 2 boiler brands and 5 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 that the water pressure in the central heating system is too low to operate safely and has shut down. (As reported on Vokera Unica HE)
Pick your boiler brand for the AL40 fix
Source
Information for the AL40 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