BoilerFaultCodes d.43 Low
Boiler Fault Code d.43
Also written as D43 — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code d.43 appears across 2 boiler brands and 17 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.
Most common meaning Your boiler is displaying a setting related to how it adjusts its heat output based on the outside temperature, but this is usually a configuration information screen rather than a functional breakdown. (As reported on Glow-worm Compact)
Pick your boiler brand for the d.43 fix
Source
Information for the d.43 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