BoilerFaultCodes 81-65 Low
Boiler Fault Code 81-65
Also written as 8165 — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code 81-65 appears across 1 boiler brand and 1 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.
Most common meaning Your boiler is still providing heating and hot water, but it has detected a problem with the temperature sensor for your solar thermal system. (As reported on Daikin D2CND)
Pick your boiler brand for the 81-65 fix
Source
Information for the 81-65 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