F.68 High

Vaillant F.68 Fault Code

Also written as F68 — same fault.

The Vaillant F.68 fault code means: your boiler is struggling to keep a steady flame alight because the gas supply is inconsistent or contains air pockets.. It appears on 33 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: Unstable flame signal error air in gas

What causes the Vaillant F.68 fault?

This fault occurs when the boiler's control system detects that the flame is flickering or unstable, making it unsafe to continue operating. The most common reasons are air bubbles trapped in the gas pipework after a service or a buildup of carbon on the sensing probe that prevents it from 'seeing' the flame correctly.

Typical repair cost £100-280 (including labour)

DIY fix possible

Check that your gas meter has credit and the isolation valve is fully openEnsure other gas appliances, like a hob, are working correctly to purge air from the pipesPress the 'Reset' button (indicated by a flame with a cross through it) once to restart the ignition sequence

Find a Gas Safe engineer

Search the official register for a qualified engineer in your area.

Gas Safe Register →

Vaillant models that show the F.68 fault code

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

Source

Vaillant F.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