Just bought my 2004 Deville. Had tint put on back windows. Now the GPS system will not work. ONSTAR says they are not able to locate me. My tint is not metallic. Did anyone with a 2004 Deville tint their back windows and not have their GPS system work. The service people said it is the wire that is in the trunk under the back dash and the Tint reflects the signal back. Now does that make sense when the tint is not metallic. Help. Thanks in advance.

The OnStar antenna needs a straight shot through the glass from the box on the outside to the box on the inside. Sounds like your tint guy forgot to (or decided not to) cut a square out of the tint for the antenna to work properly. Best bet is to return to the tint shop and have them remove the inside box for the antenna, cut a patch out of the tint, and remount the box. Should only take them a few minutes.

Here's some more info on the subject, from a tint forum:
http://www.tintdude.com/forum/index.php?showtopic=6424