K
kmillerAug 25, 2025
What to do if my Viessmann Boiler shows fault F4?
- DDonna HoganAug 25, 2025
If your Viessmann Boiler displays fault code F4 and there's no flame signal, you should inspect the ignition/ionisation electrode and its connecting cables. Also, verify the gas pressure, gas train, ignition components, ignition module, and ensure the condensate drain is clear.