How much does it cost to fix Vaillant error code F.56?

Typical repair cost for the Vaillant F.56 fault is £150-300 including labour.

F.56 High

Vaillant F.56 Fault Code

Q: What does the Vaillant F.56 fault code mean?

Your boiler has detected a problem with the way it manages the gas and air mixture required for safe combustion, causing it to shut down to prevent unsafe operation.

Also written as F56 — same fault.

The Vaillant F.56 fault code means: your boiler has detected a problem with the way it manages the gas and air mixture required for safe combustion, causing it to shut down to prevent unsafe operation.. It appears on 11 Vaillant models in our database.

Technical description: Combustion component fault

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 F.56 fault code

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

Source

Vaillant F.56 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