As long as you have power to the window itself....and yes you will need to remove the access panel in the inside of the T gate to check for power there.....and to see if the both wires have not broken off.
If all is well in there, take your multi tester and check along each of the 14 metal stripes going across the glass. Just do a continuity test, and look for spots where the metal paint/tape is damaged and there is no continuity. Its very helpful if your multi-tester had a audible tone when it does detect continuity.
Permatex sells a repair kit that includes parts to reattach to the glass, and the conductive paint with stencil.
They sell two kits I am not too sure this one has the repair to reattach the wires to the glass, but it does have the conductive paint.
http://www.midwayautosupply.com/detailedpr...iption.asp?9369