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 its flame steady, which is preventing it from staying on and heating your home.. It appears on 19 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: Fault: Flame signal unstable - Flame monitor reports an unstable flame signal

What causes the Vaillant F.68 fault?

This fault occurs when the boiler's control system cannot detect a consistent, healthy flame after the burner has ignited. The most common reasons are a worn-out sensing probe that can no longer 'see' the flame, or a gas valve that isn't delivering a steady flow of fuel to keep the burner lit.

Typical repair cost £100-250 (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 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 7 July 2026