d.65 High

Vaillant d.65 Fault Code

Also written as D65 — same fault.

The Vaillant d.65 fault code means: your boiler is failing to light because it cannot detect a flame within the time limit allowed, which usually suggests a problem with the gas supply or the ignition process.. It appears on 25 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: Maximum ignition time s
Typical repair cost £150-300 (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.65 fault code

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

Source

Vaillant d.65 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