During the mid-1980s, American car manufacturers switched from using sealed-beam headlights to aerodynamic headlight assemblies that were made from high-impact plastic. These new aerodynamic headlights contained replaceable bulbs, meaning that the whole headlight did not have to be replaced every time a bulb burned out. The old sealed-beam units were made from glass and the entire headlight had to be changed when it burned out. However, the headlight lens usually stayed clear throughout the lifespan of the unit. The modern plastic headlights, on the other hand, are prone to clouding over when they age and are expensive to replace. However, there are a few home remedies that you can perform on your headlights to restore their luster.
Many auto parts stores now carry headlight restoration kits. Kits are made by many different manufacturers and usually contain a buffing pad, an attachment for your power drill, buffing compound made especially for plastic and instructions. If you use one of these kits, it is recommended that you protect the surrounding painted area around your headlight with painter's tape. The compound used and the high-speed turning of the buffing pad may cause damage to other surfaces.
If you do not wish to purchase a restoration kit or if you do not own a power drill, you can save some money and get good results with automotive wet/dry sandpaper, a spray bottle with water, rubbing compound or other polish and some microfiber cloths. Using sandpaper on your plastic headlights may seem harsh, but the grit on this type of automotive sandpaper is very fine, ranging from 800- to 2,000-grit. Remove all the imperfections and pits caused by rocks with the lowest grit paper, keeping the area wet with a spray bottle. The headlight surface will get smoother and clearer with each graduation of sandpaper, up to the highest grit. Polish the headlight surface to remove the fine scratches from the sandpaper. This method takes a lot of time and elbow grease, but it is effective.
Some plastic headlight lenses may be too far gone for any home remedy to correct. In this instance, the replacement of the headlight lens, or assembly, is in order. Replacing a headlight assembly is not as complicated as it sounds. The owner's manual of your particular vehicle may have all of the information you need. Open the manual to the bulb replacement section, since some headlight assemblies need to be temporarily removed from the vehicle to replace a faulty bulb. Simply place the bulb back into the new headlight assembly and affix it back to the vehicle, following the directions in the manual. If your owner's manual does not specify how to remove the headlight assembly, purchase a repair manual (available at auto parts stores) for your vehicle.
