Removing the haze
Most cars and a lot of trucks today are manufactured with headlamp assemblies that use quartz-halogen bulbs plugged into the back of a large plastic reflector. The outer surface of these headlamp modules is molded polycarbonate plastic. That plastic is much lighter than glass and far more resistant to stone chips and cracks. However, after a few years of exposure to sunlight and atmospheric chemicals, polycarbonate has a tendency to get hazy. Severely neglected lenses can actually pit and develop a network of fine cracks, called craze, which makes the job of fixing them tougher. It’s worth a shot, though—and you’ll need only a few bucks’ worth of materials to get the job done.
Fortunately, there’s a simple and inexpensive solution. Unlike glass, the polycarbonate plastic can be polished back to a surface as smooth as new, in a procedure that won’t take more than a half-hour.
Mask off around headlights
Buy some good 2 inch masking tape. Mask the area around the headlamp that needs to be polished.
Buffing the headlamps
You can buy a prepackaged kit intended specifically for the task restoring headlamps. 3M and Permatex both sell a kit containing everything you need for around 10 bucks. Any auto parts store will carry them. You can also buy the sandpaper and polishing compound individually. If you only need to do one pair of headlights, it’s cheaper to buy the kit instead of the sandpaper one sheet at a time.
Sanding the headlight.
Soak a piece of 1000-grit wet/dry sandpaper in cold water for 10 minutes. Lightly sand the lens in straight strokes. Methodically cover the entire lens surface, always sanding back and forth in one direction. Keep the surface wet while you work. Again, be careful not to damage nearby paint or trim.
Sand until the pits, discoloration and scratches you’re trying to eliminate are gone. Don’t rush this part. And don’t be afraid to dry the surface with a towel and check the uniformity of your sanding. When you’re done, clean and dry the area.
Now perform the same operation with 1500-grit wet/dry sandpaper, this time sanding at right angles to your previous work. Again, be methodical. Keep the paper wet, cover the entire surface and then clean up to remove any abrasive powder. Repeat the procedure, every time at right angles to the last sanding, with 2000-, 2500- and 3000-grit wet/dry. If you don’t have 2500 or 3000, it’s fine, you’ll just have more buffing to do. Clean up all the sanding residue and dry the area.
Now go back to your compound and flannel to hand-polish out the scratches. Your lens should look like new—shiny and clear.
Clean up every last vestige of the abrasive polishing compound. Now wax the lens thoroughly with a paste car wax. This last step will keep acid rain, dirt and road salt from attacking the plastic, at least for a while. You can make it even better by applying an aerosol clear made for headlights. The factory headlights come with a clear to protect from ultraviolet rays. It will make your work last much longer.