I can check from ELSA. Heating is not controlled by voltage, it's controlled by CAN. I don't think the pins 4 and 7 are connected actually anywhere. All the pinouts I've seen only have 6 pins defined.
Edit :
Unfortunately my ELSA stops at model year 2016. That only has 6 pins connected from the 8 and has been like that since March 2012. Probably the new features introduced for >MY2017 for the front assist require the 4 and 7 to be connected as well, I don't know, sorry.
You can buy time from
Erwin and print the diagrams for that car. Only about 7 € / hour so you'll easily print the diagram and some other stuff as well in that one hour.