I just picked up a 97 town car. The rear view mirror was detached from the mount. Any ideas on how to reinstall with the compass unit?

There is help in the link. The general consensus is if neither work, you need a new mirror.

https://www.google.com/search?q=2015+GMC+ACADIA.+Compass+and+temperature+won%27t+work+in+my+rear+view+mirror

..

You need to remove the plastic plate that cover the mirror joint from the inside and undo the three bolts.

Owners Manual....

They make the mirrors with several styles of fasteners. Usually there is a screw "plug" called a set screw. This usually has a Hex shaped recess in the part and you simply insert a Hex key and lightly snug the set screw by turning it clockwise like most screws you would be tightening.

The reason I said "lightly" is that the part that is on the windshield is glued on. They are forever coming detached from the windshield. So reefing on the set screw will probably cause the glue to fail. It is better to have to tighten the mirror several times a year than to have to get a glue kit and remount the base to the windshield.

There is also a mount which depends on a spring tab beneath the mirror to lock the assembly in place. If you have this type of mount, it is not adjustable. But you might be able to put a drop of glue on the surface seam to take out the rattle and the mirror should no longer vibrate.

I hope my info helps you.

http://www.ehow.com/how_5449679_remove-rear-mirror-mount.html

remove trim panel, remove mirror fasteners.

Glass, Outside Mirror—Town Car

Removal and Installation

1. Push upper edge of outside rear view mirror glass (17K707) into the outside rear view mirror to expose latch release.
   

1. Using a small flat-bladed screw driver or equivalent, move latch release to released position.
   

1. Remove outside rear view mirror glass mounting back and outside rear view mirror glass from outside rear view mirror.
   

1. Disconnect heater wire connectors and auto dimmer connector, if equipped.
   

1. To install reverse Removal procedure.
   

------------------------------------------------------------
Mirror, Power—Outside Rear View
Town Car

Removal and Installation

1. Disconnect battery ground cable (14301). Refer to Section 14-01 .
   

1. Remove front door trim panel (23942). Refer to Section 01-05 .
   

Trim Panels, Door Front—Town Car
Removal

1. Snap out two door pull strap retaining screw covers. Remove screws.
   

1. Remove three screws on front and rear side and center of front door trim panel (23942).
   

1. NOTE: The following procedure must be used during removal and installation of the door armrest and trim panel. Refer to the appropriate illustrations for component and vehicle model identification.
   
   Using the Trim Pad Removing Tool from Rotunda Windshield and Moulding/Trim Removal Kit 107-R0401 or equivalent, pry the trim panel retaining clips from the door inner panel.
   

1. NOTE: Do not use front door trim panel to remove trim clips from door inner panel. Replace any bent, damaged or missing push pins.
   
   Remove window regulator control switch housing from front door trim panel. Lift up housing in front and disconnect all connectors.
   

1. Disconnect wiring harness and heated seat switch electrical connectors if equipped.
   

1. Remove the door trim panel.
   

1. Disconnect two electrical connectors.
   

1. Remove nut from outside rear view mirror mounting base.
   

1. Swing outside rear view mirror (17682) toward driver door window glass to expose screw in mount base.
   

1. Remove screw from outside rear view mirror base.
   

1. Remove outside rear view mirror from front door (20124). Guide wiring and connectors through hole in front door.
   

1. To install, reverse Removal procedure. Tighten nuts to 8-10 Nm (71-88 lb-
   

Insufficient information

there is nothing the shop did the that caused this they do that because of the heat inside the car sitting out in the sun

you could always try unplugging the battery for about ten minutes to see if that resets it. make sure you have the code for the stereo first if it requires one.

Go to Auto Zone or any other auto place and buy some rear-view mirror adhesive its a kit with a cleaner and a clear glue it Works will re-attach mirror. Good Luck