BoilerFaultCodes 40-50-70 (ll-ll-ll) High
Boiler Fault Code 40-50-70 (ll-ll-ll)
Also written as 405070LLLLLL — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code 40-50-70 (ll-ll-ll) appears across 1 boiler brand and 4 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 faulty sensor that monitors the temperature of the water used for your taps, causing it to stop producing hot water to prevent overheating. (As reported on Ariston Genus 30 Plus)
Pick your boiler brand for the 40-50-70 (ll-ll-ll) fix
Source
Information for the 40-50-70 (ll-ll-ll) 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 27 April 2026