I have the Onstar in my H3 as part of the mirror with compass and temperature. To "change the compass zone" as described in the manual does not seem to apply to this mirror. If I press and hold the on/off button, instead of the COMP button (which it doe not have) all I can change is Farenheit or celcius. Any ideas?

I have changed the zone in mine and did it according to the Owner's manual. I held in the On/Off button for about 6 or seven seconds (Owner's manual says 5), and it switches to Zone settings.
It has to be pressed all the way in. If it fails to work, take it to the dealer and have a new one installed.

Easy button! I read the instructions a few times. Take a deep breath..

Drive out onto a frozen lake.....way out on it. Then call Onstar and tell them you are lost and do not know where to go. Ask them to give you the name of your location. "ummm sir...you are in a lake" My frined thinks that is funny.