Boiler Fault Code d.44

Also written as D44 — same fault.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 31 August 2026

Fault code d.44 appears across 3 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 real-time measurement of the flame signal, which is a diagnostic check rather than an active error, but if it is persisting, it indicates the system is struggling to confirm the burner has lit correctly. (As reported on Vaillant Ecomax Condensing 600/800 series)