Green wire with a white strip in the overhead unit is switched power. use the V1 wire tap and rn the power cord between teh headliner and windshield to right above the mirror. Then you can install your V1 above your rear mirror and you'll be all set. Takes less than 15 minutes. I have hardwired the V1 in 3 E70's of ours.

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2013 Cayenne GTS Basalt Black/Alcantara (Wife's Daily Driver)
2013 Porsche 911 cab Aqua over pebble and agate (My daily driver)
2010 Porsche GT3RS Black Grey/Black Alcantara (Track car)
2012 Porsche CaymanR Peridot Green with carbon sport buckets (Wife's Track car)