I can view the wiring diagrams for the '06 but not the '07 or '08.
The diagram shows Black, Grey, and Dk Blue/White (3 wires). This is regardless of OnStar. The portion of the diagram mentioning OnStar shows an extra tap from the Black wire (gnd) within the mirror. No mention is made of the Autodim or compass features (self contained?).
Hope this helps.

 

I just checked my paper work from purchase on 07/19/07.

DD8 - Mirror, Inside, w/auto dim & compass

 

DD8 is the option code?

 

An auto-dimming rearview mirror is great idea. I had it in my minivan. Unfortunately, no one thought about auto-dimming side mirrors. Bright headlights in those side mirrors are almost blinding. I usually just slow down and hope the vehicle passes me.

 

I don't like the dimming feature. I have the mirror that dims and has the compass and no On-Star. I'd like to turn off the dimming function. I can do this each time I get into the car, but hate to have to do it. The windows are already tinted and dimming the mirror makes the cars behind me seem only like white dots. Any suggestions how to turn this feature off?

 

Try pulling under hood fuse 21.

 

Or sell me the mirror......

 

Put a piece of black tape over the light sensor on the mirror. I don't know if your sensor is behind the glass or under the mirror, but it will usually be about 1/4" in diameter.

 

I just purchased a used 2007 and the mirror is the auto dim without on star

but

the only plug hanging down is a three wire so it won't plug in at all

 

Have a '07 with auto dim and compass. Is it a direct replacement for the OEM mirror w/auto dim, compass, + Temp? Thanks in advance for your help.