d.39 Low

Boiler Fault Code d.39

Also written as D39 — same fault.

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed

Fault code d.39 appears across 2 boiler brands and 14 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.

Most common meaning Your boiler is reporting a reading from a solar heating component, which is likely just an informational status check regarding the temperature of water coming from a solar panel system. (As reported on Glow-worm Energy7 Combi)

Pick your boiler brand for the d.39 fix

Glow-worm d.39 5 models Vaillant d.39 9 models

Source

Information for the d.39 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