F.97 High

Vaillant F.97 Fault Code

Also written as F97 — same fault.

The Vaillant F.97 fault code means: your boiler's internal computer has failed a self-test and is no longer able to communicate with the rest of the system.. It appears on 14 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: Main PCB self-test failed. Main PCB defective

What causes the Vaillant F.97 fault?

This fault occurs when the boiler's central control board fails its internal safety checks during startup or operation. The most common reason is a hardware malfunction within the circuitry, often caused by a component reaching the end of its lifespan or suffering damage from an electrical power surge. Because the board can no longer safely manage the gas and ignition process, it shuts the system down to prevent any hazards.

Typical repair cost £300-£550 (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.97 fault code

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

Source

Vaillant F.97 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