D.68 Medium

Vaillant D.68 Fault Code

Also written as D68 — same fault.

The Vaillant D.68 fault code means: your boiler is struggling to light its flame on the first try, which could cause it to lock out if it fails repeatedly.. It appears on 26 Vaillant models in our database.

Book a service

This fault should be looked at by a Gas Safe engineer within the next week or two. It may get worse if left.

Technical description: Unsuccessful ignitions in the first attempt

What causes the Vaillant D.68 fault?

This fault occurs when the boiler's internal computer detects that the gas didn't ignite correctly during its first starting sequence. It is often caused by a build-up of carbon on the spark electrodes or a supply issue that prevents the correct amount of gas from reaching the burner. While the boiler may try again and eventually fire up, it indicates that the ignition system is becoming unreliable.

This fault can be more frequent during the first cold snap of autumn, as electrodes and gas valves that have sat idle over summer may struggle to perform under the increased demand.

Typical repair cost £100-280 (including labour)

DIY fix possible

Check that your gas pre-payment meter (if applicable) has enough credit.Check that other gas appliances, like a hob, are working correctly to ensure there is a gas supply.Try restarting the boiler by pressing the reset button (usually marked with a flame or 'X').

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Vaillant models that show the D.68 fault code

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

Source

Vaillant D.68 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 27 April 2026