BoilerFaultCodesVaillant 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 1 Vaillant model in our database.
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.
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 7 July 2026