To repair a broken car window, start by checking the fuses. Look for one with a broken metallic strip in the center, which indicates that it is blown and should be replaced. Check the wiring around the fuse box, and tighten any loose connections. Try cleaning the window switches with rubbing alcohol. If this does not work, remove the door panel, and inspect the motor for problems. Contact a mechanic if none of these solutions solve the problem.
If the mechanics of the window are working fine but the glass is cracked or smashed, the window needs to be replaced. This can be done at home or by a mechanic. To perform the task at home, start by cleaning up any shattered glass using a shop vacuum. Contact an auto dealer or search auto salvage yards for a window with compatible dimensions.
Remove the inner door panel, and carefully take off the plastic vapor-barrier sheet. Raise the windows so the bolts holding the broken glass in place line up with the access holes in the steel. Vacuum any remaining glass from the inside of the door. Take off the seal found at the window's bottom, and open the slot where the glass panel is inserted.
Lower the shorter side of the glass into the slot at a 90-degree angle, and once the long side of the glass catches in the slot, pull the short side up and in place. Reattach the bolts to hold the window in place, and make sure it is able to move up and down. Reassemble the door.