Viessmann Vitodens 050-W fault F9
Fan speed too low during burner start
Gas boilerWhat it means
Burner enters a fault state because the fan speed is too low during the burner start sequence.
Likely causes
- Faulty fan
- Faulty fan connecting cables
- Fan power supply fault
- Fan control fault
- Fan speed too low during burner start
Where to start
- Confirm control unit has issued a heat demand (displayed)
- If fan does not start after approx. 1 min, fault F9 is shown
- Check the fan connecting cables
The full answer, free
- 16 more checks in order
- The readings and component tests from the manual
- How to put it right, step by step
- The manual page for this fault (page 57), right under the answer
Safety: Isolate gas and power before you open the case. If you have been into the gas side, do a tightness test, and a combustion and flue check before you hand back. Gas Safe (UK) or RGI (Ireland) work only.
From the Viessmann manual for the Vitodens 050-W. Check the model on the data plate before you order parts.