Replace a side window on a car by removing the inner door panel and vapor barrier sheet, lowering the window-height mechanism, peeling back the window seal and freeing the window tracks. Slide the new glass into place starting at the short side, and replace all the components.
First, pry off the door trim to find the screws holding the door panel in place. For a newer-model car with power windows, disconnect the plug that delivers power to the door and windows located in the door panel. You may need to consult your service manual. Next, carefully peel away the plastic vapor barrier, making sure not to rip or stretch it.
Now you can see the window height regulator. Raising or lowering this regulator aligns the screws holding the window in place with the holes in the door's steel frame. Remove the screws, and lift out any pieces of glass still in place. Vacuum any glass shards from the door before replacing the window.
Peel back the seal at the bottom of the window, and free the window tracks to help guide in the new piece of glass. Slide the glass along the tracks starting on the short side until it reaches the regulator. Replace the bolts of the window height regulator, and return it to its regular position. Replace the window seal, vapor barrier and door panel.