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 12 Vaillant models 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.
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.97 fault code
Click a model for the full fault code list and model-specific repair notes.
- ecoTEC plus Repair: £300-£550
- ecoTEC Plus 615 Repair: £300-£550
- ecoTEC Plus 620 Repair: £300-£550
- ecoTEC Plus 625 Repair: £300-£550
- ecoTEC Plus 630 Repair: £300-£550
- ecoTEC Plus 635 Repair: £300-£550
- ecoTEC Plus 65 Repair: £300-£550
- ecoTEC Plus 832 Repair: £300-£550
- ecoTEC Plus 836 Repair: £300-£550
- ecoTEC Plus 840 Repair: £300-£550
- ecoTEC Plus 938 Repair: £300-£550
- ecoTEC sustain Repair: £300-£550
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 27 April 2026