F15
Viessmann
Control bus communication fault
Communication error between main control and user interface or external Vitotronic module
Advertisements
Safety Warning
This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.
If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.
Advertisements
Possible Causes
Loose KM-BUS or LON bus connectors, Damaged communication cable, Incorrect module addressing, Faulty Vitotronic control module
How to Fix / Troubleshooting
Safety: Turn off power before working on control wiring.
- Check connectors: Open the control compartment and locate the KM-BUS or communication terminals. Ensure all plug-in connectors are fully seated.
- Inspect cable: Follow the low-voltage cable to the remote control or Vitotrol room unit. Look for damage, pinching, or water ingress.
- Module reset: Power down the boiler and any external modules for 30 seconds, then power back up to reset communication.
- Addressing: On systems with multiple Viessmann modules, verify that addressing switches (if present) are set according to the installation manual.
- Persistent F15: If the error remains, a technician should test the bus with diagnostic tools and replace the faulty module or cable.
Advertisements
Repair Difficulty
Medium
3/5
Required Part
Vitotronic Control Module
Check Price on Amazon
We may earn a commission from links on this page.
Advertisements