d.50 Low

Vaillant d.50 Fault Code

Also written as D50 — same fault.

The Vaillant d.50 fault code means: your boiler is displaying an internal message regarding how slowly the fan is spinning, which usually means the system is attempting to calibrate itself but may need a professional adjustment.. It appears on 25 Vaillant models in our database.

Monitor it

This is a minor fault. Keep an eye on it and mention it at your next annual boiler service. Reset the boiler and see if it clears.

Technical description: Correction of the minimum fan speed
Typical repair cost £90-180 (including labour)

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.50 fault code

Click a model for the full fault code list and model-specific repair notes.

Source

Vaillant d.50 fault code information on this page is sourced and cross-checked against the official Vaillant service / installation manuals for each affected model.

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