HVACopediaViessmann · Boiler
Connection error Display link lost to HMU
What the display is showing
Shown with the fault symbol when the touchscreen unit cannot talk to the heat management unit.
Applies to: Vitodens 200-W B2HE 85, 120, 150, 199
What to do
- Check the cable and plug between the HMU and the HMI programming unit.
Models that show this code
4 models in Vitodens 200-W B2HE
Other codes on the same units
- A.12 Real-time clock battery flat
- A.18 Possible condensate back-up in heat cell
- A.19 Temperature limiter has responded
- A.20 Service interval could not be activated
- F.100 PlusBus voltage error
- F.104 External fault message input active
- F.11 Solar collector sensor open circuit
- F.12 Solar collector sensor short circuit
Save it for the next call
Star this code in the HVACopedia app and keep the whole library on your phone for jobs with no signal.
Source: Viessmann Vitodens 200-W B2HE 85/120/150/199 Service Instructions 6167 813-24 (09/2026), Fault display, p.60. Summarized in our own words; check the original manual for your model.
For licensed technicians. Gas, electrical and refrigerant work must be done by a qualified, licensed person. Shut off power and gas before servicing, never bypass a safety control, and follow the manufacturer’s manual for the exact model; it and local codes always take priority. HVACopedia is not affiliated with any manufacturer; brand and model names only identify the equipment.