I recently got my 79 back from paint and the drivers (elec) window would not go down all the way. Short story, it was caught on the mirror cable and a wire harness. Somewhere on this site I found there is an access panel on the hinge end of the door, inside find two holes for looping the remote control out and back in. ( Thanks to whoever wrote it, I did not mark it down.) I used mechanical fingers and string to untangle the harness and cable (pulled cable backward) and then to pull the cable near the first hole so I could grab it. ( I knew GM had to have a system but what was it?) After that it was back through the inside hole and out the opening for the door panel. The glass goes all the way down now, the mirror doesn't try to move when lowering it. Thanks.