If a window on your Mustang won't move up or down, it's an indication that the window regulator on your door has become damaged. In order to solve this problem, you need to remove the window regulator from your door, and replace it with a new one. You can pick up a window regulator that will fit the door of your Mustang from your Ford dealership or a local auto parts retailer.
Use the trim stick to remove the trim from around the door handle. Lift the trim away from the door. Remove the two screws which hold the door handle in place with a Phillips-head screwdriver. Remove the handle from the door.
Remove the trim from the door panel inside the door. Lift the trim away from its connectors on the door and pull it away. Remove the mounting screws and lift the panel off the door.
Use a hex wrench to remove the two bolts which connect the glass pane to the window regulator. This will disconnect the window from the regulator. Place a wooden block underneath the window, to prevent it from falling and breaking.
Remove the lower mounting -- which affixes the window regulator to the door -- using a wrench. Lift the regulator off the door and discard it in the trash.
Secure the new window regulator onto the door with the mounting bolts. Align the bolt holes on the window with those at the top of the regulator, and attach two hex bolts between them. Reattach the door handle and door panel and secure them with screws, using a screwdriver.
