I am very pleased with the V1 installation I've made on my US SLK55. I removed the panel under the glovebox and connected the V1 power supply to the passenger footwell 12V Accessory Plug wiring which goes on and off with the ignition -- I can leave the V1 switched on all the time and it turns on and off with the ignition. Wiring (telephone cords) to the V1 main unit and the remote are almost completely hidden and the remote mounts perfectly between the tach and speedometer.
Sorry for the poor quality of the photos, but I think they will be good enough to provide some help.
Here you go:
-Remove the passenger-side floor mat.
-Remove 3 T20 Torrx screws holding the black panel under the glove box
-Pull rear edge of black panel to in front of the carpet at the firewall
-Insert a large screwdriver from below under the bottom edge of the side of the black panel near where the 12V outlet is mounted. Pry out the spring connector to release the panel (SEE PHOTO)
-Swing panel down and out enough to give access to electrical connections
-Squeeze and disconnect the electrical connector from the footwell light
-VERY CAREFULLY pry off the L-shaped connector from the back of the 12V outlet (SEE PHOTO)
-Strip and solder + and - connectors to for the V1 powersupply or other unit. On my US SLK55 the ground wire is brown; the Positve 12V wire is Black/Yellow.
_Mount the V1 on the desired location (for me this is beside the rear view mirror, high on the windshield). Measure the length of wiring you need before starting the wire installation to be sure you have enough wire. Route the phone-line for the V1 main unit along the backside of the A-pillar cover and behind the moulding at the top of the windshield.
-Mount the V1 Remote between the tach and speedometer -- it is a perfect fit and does not even require any Velcro or similar to hold it in place (SEE PHOTO). Measure the wire length before starting the routing. Route the phone line for the V11 remote in the tight gap between the brushed aluminum piece and the padded dash piece just above the ignition switch and then down along the seam with the center console. Pry off the spring connector for the black panel on the driver side (as above for the passenger side, PHOTO) and route the phone line through that area. Reach through from the passenger side into the center of the dash behind the Climate Control for the remote's phone line and pull it through to connect it to the power supply.
-Reassemble in reverse order. Put the black panel under the glove box up and in the general area of final location before connecting the 12V electrical connector because the wires may limit your ability to wrestle the panel in place.
-Check operation of the V1 and the Accessory Plug before snapping the panel info place and installing the screws.
-You should have a very clean installation with only a short pice of wiring sowing above the steering wheel.
Hope this helps.