D.033 High

Vaillant D.033 Fault Code

Also written as D033 — same fault.

The Vaillant D.033 fault code means: your boiler is struggling to get its internal fan to the right speed, which means it cannot safely vent exhaust gases, so it has stopped working to keep you safe.. It appears on 7 Vaillant models in our database.

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description: Fan speed target value
Typical repair cost £180-350 (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.033 fault code

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

Source

Vaillant D.033 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 7 July 2026