Verified boiler fault code
Viessmann F6 Fault Code (Viessmann fault-code checker — all-boiler row)
Fan not at standstill / plug-in connection.
Safety disclaimer
Fault code summary
- Manufacturer
- Viessmann
- Fault code
- F6
- Fault type
- Fan, Electrical
- Severity
- high
- Reset
- Not specified
- Applicable models
- All Viessmann boilers
Quick answer
Fan not at standstill / plug-in connection.
What does this fault code mean?
Fan not at standstill / plug-in connection.
Common causes
- Fan not at standstill or plug-in connection fault.
Symptoms
- Burner in fault mode or emergency operation.
What can the homeowner safely check?
This information was not provided in the verified manufacturer source.
Boiler reset information
Reset information was not provided in the verified manufacturer source. Do not repeatedly reset an unresolved fault.
When should I call an engineer?
Contact a suitably qualified heating engineer when the fault persists, the boiler locks out, or the manufacturer instructions do not resolve it. For gas appliance work in the UK, use a Gas Safe registered engineer.
Engineer diagnosis
- A Viessmann-trained installer should assess fan feedback and plug-in connections.
Applicable boiler models
Related fault codes
No related verified fault codes are available for this range.
Manufacturer documentation
Viessmann UK Fault CodesFault Code F6, 58, F9, F-E1, F-E2 and F-F6 | All Viessmann boilers | Burner in fault mode / Emergency operation | Fan not at standstill / plug-in connection
Last verified
2026-09-12
Frequently asked questions
What does Viessmann F6 mean?
Fan not at standstill / plug-in connection.