D.44 Medium

Boiler Fault Code D.44

Also written as D44 — same fault.

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed

Fault code D.44 appears across 3 boiler brands and 20 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.

Most common meaning Your boiler's electronic system is struggling to correctly detect the flame signal, which could lead to it locking out for safety. (As reported on Vaillant ecoTEC)

Pick your boiler brand for the D.44 fix

Glow-worm D.44 1 model Heatline D.44 6 models Vaillant D.44 13 models

Source

Information for the D.44 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