I have a auto dimming mirror and I only have the wireing that is on the mirror itself not the part that is connected to the car and all the wires are black.If I unplug the connection on the back of the mirror then unclip the other end of the small harness from the mirror the wires are numbered 1-2-3.What I need to know is what wire is power,ground and backup disable.There are a couple of threads about what wires are which but they all refer to wire color which I dont have,just1-2-3.Any help would be great.