[f5fstop]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by theadlee:
f5stop,

I tried the light green wire in the A-pillar like you mentioned and I got nothing. I even tested it with my volt meter in park and reverse and there was no change on this wire. I got to thinking, why would the rear view mirror need to know when the H3 in reverse? Maybe there is some feature that my H3 does not have on the mirror. My mirror does nothting different when the H3 is in reverse.

I endend up running a wire to the engine compartment and tapping in there. Works great now. </div></BLOCKQUOTE>

My fault, I didn't follow the diagram from backup lamps all the way over to mirror. For some ODD reason, the wire color changes at splice 224. It is lt green from the backup lamp switch to the rear backup lamps, but for some really weird reason, that I can't comprehend, it changes to brown at the splice and goes to the mirror.
Sorry for the wild goose chase. GM surprises me everyday....

As for what the mirror does in reverse....if you have the auto dimming mirror, it un-dims in reverse at night, and the module inside the mirror requires a reference (12V) signal to notifiy the module that you have now shifted into reverse.
I believe the auto-dimming mirror is standard, but I might be mistaken.