Garage door windows need to be replaced as soon as possible if they are broken. Unlike a standard house window, the garage door window is part of a moving structure, and it is likely to drop broken glass. To replace a window, a pair of protective gloves, a rubber mallet, a tape measure, and a ladder are needed. Part of the procedure is a two person job.
The first step, and the most important, is to remove power if the door has an opener. Unplug the power cord from the overhead electrical outlet.
The next step is to remove the screws which secure the window frame to the door in insulated doors. For non-insulated doors, remove the retainer snaps from the frame. Have the second person hold the window frame to the door from the outside while the screws or retainer snaps are removed. Remove the screws/retainers snaps from the top of the door first, and then proceed to the sides, and then the bottom.
Carefully clear any remaining glass out of the frame, starting at the top. The frame can be pulled from the door to do this. Measure the inside height and width of the frame. Subtract 1/16 inch from each dimension and purchase a single strength plane of glass.
Insert the frame into the garage door from the outside. Ask your helper to hold the frame flush against the door. Place the glass into the window frame and secure the inner retainers with the retaining screws if your window frame uses screws.
Insert the frame into the door from the outside, with the second person holding it flush. Place the glass into the frame and secure with the screws/retainer snaps. If snaps are used, press as far in by hand as possible, then tap gently in with a rubber mallet.
Lastly, plug the power cord into the overhead outlet if the door is controlled.