Hi guys - I'm planning on installing two Blackvue DR-750S cams in a Nissan Frontier and a BMW 335i. I want to use mirror tap cables for both installs. On the Nissan all I have is the auto-dimming/compass/temp cable, but on the 335i there's also a rain sensor cable. Which should I use on the 335i? And here's the dumb part - will the car's mirrors still work properly after I've tapped their cables? And how does the cam know how to draw the right amount of power when not using its factory power cable? Also seems like an auto dimming mirror wouldn't supply enough power for a dash cam.