BoilerFaultCodesVaillant d.44 Fault Code
Also written as D44 — same fault.
The Vaillant d.44 fault code means: 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.. It appears on 10 Vaillant models in our database.
Technical description: Actual ionisation–current value
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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Vaillant models that show the d.44 fault code
Click a model for the full fault code list and model-specific repair notes.
- ecoMAX Repair: £120-250
- ecoMAX 613 Repair: £150-250
- ecoMAX 618 Repair: £150-300
- ecoMAX 622 Repair: £120-250
- ecoMAX 635 Repair: £150-300
- ecoMAX 824/2 E Repair: £150-250
- ecoMAX 828/2 E Repair: £150-250
- ecoMAX 835 E Repair: £150-250
- Ecomax Condensing 600/800 series Repair: £120-250
- ecoTEC plus VU GB 656/4-5 A Repair: £150-300
Source
Vaillant d.44 fault code information on this page is sourced and cross-checked against the official Vaillant service / installation manuals for each affected model.
- Vaillant Ecomax Condensing 600/800 series manual (PDF)
- Vaillant ecoMAX 835 E manual (PDF)
- Vaillant ecoTEC plus VU GB 656/4-5 A manual (PDF)
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 31 August 2026