BoilerFaultCodesViessmann F9 Fault Code
The Viessmann F9 fault code means: your boiler has stopped working because the internal fan isn't spinning fast enough to safely start the heating process.. It appears on 9 Viessmann models in our database.
Technical description: Burner in fault position. Fan speed too low during burner start. Check the fan, the fan cables and the power supply to the fan.
What causes the Viessmann F9 fault?
This fault occurs when the boiler's computer tries to start the heating process but detects that the internal fan isn't spinning at the required speed to clear out exhaust gases. The most common reason is a mechanical failure within the fan motor or a communication issue where the control board can no longer send power or instructions to the fan.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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Viessmann models that show the F9 fault code
Click a model for the full fault code list and model-specific repair notes.
- Vitodens 050-W Repair: £250-£550
- Vitodens 050-W BPJD Repair: £250-450
- Vitodens 100-W Repair: £150-350
- Vitodens 100-W WB1A Repair: £120-200
- Vitodens 100-W WB1B Repair: £250-450
- Vitodens 111-W Repair: £200-450
- Vitodens 222-F Repair: £250-£550
- Vitodens 242-F B2UA Repair: £250-450
- Vitodens 242-F FB2B Repair: £200-450
Source
Viessmann F9 fault code information on this page is sourced and cross-checked against the official Viessmann service / installation manuals for each affected model.
- Viessmann Vitodens 050-W BPJD manual (PDF)
- Viessmann Vitodens 100-W manual (PDF)
- Viessmann Vitodens 100-W WB1A manual (PDF)
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026