I read previous threads that said i would need an onstar adapter if i want to install a new stereo in my 2007 h3 but i dont use the onstar feature. is the adapter needed for proper installation or just to keep onstar working? can i install the stereo without the adapter with no problems?

 

It's also for the door "ding" when it's open, if you don't care about that you should be fine. Also the Bluetooth won't work but I've seen other install a new mic where OEM one is.

 

He's right, the adapter gives you an audible door chime thru your speakers.

I don't use my OnStar, either. What I did do was what he metioned previously as well. I routed my microphone/wire for the hands-free-device coming off my touch screen under my dashboard, up the driver's side pillar and then cut a hole thru the insullation foam to let it sit in the small factory vent cup where the OnStar microphone is. I just pushed the OnStar microphone forward a little to make room. People say I come off very clear when driving at highway speeds.

I'm pretty happy.