BoilerFaultCodes 12-66 Low
Boiler Fault Code 12-66
Also written as 1266 — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code 12-66 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 having trouble detecting the steady flame it needs to run safely, but it may just be a temporary sensing error. (As reported on Daikin D2CND)
Pick your boiler brand for the 12-66 fix
Source
Information for the 12-66 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