auto dimming rearview mirror

Hello and thanks in advance for any help I receive. I have a 99 grand prix gt. It had a basic auto dimming rearview mirror(no compass or temp just auto dim).At the end of the summer the liquid leaked out and became cloudy it didnt work anymore. So i just bought a new universal one off Ebay for $30bucks. Pretty nice unit and only has 3 wires just like my old one. One supposed to be batt. one supposed to be acc and one is ground. Problem is I checked my wiring with a tester and the yellow wire in the headliner is the acc it is ok. black is obviously ground and the green one i assumed was batt. but it only gets power to the green wire when i put car in reverse! Weird! What could possibly be the connection between the wiring for the mirror have to do with the transmission? its a floor shift so why would a wire run from the console on the floor to the headliner? Looked for short couldnt find anything.Does anyone know a link where i can view a wiring diagram for this car? Thanks again!

It is not weird at all but normal. Because it needs to know when the autotransaxle is in reverse to perform the clear function. Battery voltage is applied to the mirror reset terminal via the green wire. Then the mirror at least the stock one changes gradually to a clear state for better visibility when backing up.

Wow! I never would've figured that one but thanks alot BNaylor! I guess to make my new mirror work as it is supposed to I will have to run a wire from the fuse panel to make the batt connection and just tape off the original green one in the car.Thanks again!

You're welcome.

Sounds like a good plan to me. :thumbsup:

hello i am adding an auto dimming miror with compass and temp, any one know where the wiriing goes, where the grean wire goes to the shifter, also i was told that the compass part is built in and requires only one of the extra wires, but the temp needs an outside sensor, is that all or does it also run through the computer, thanks for any help