Dim headlights cause unsafe driving. I really did not need to tell you that. You don't always know realize the headlights are becoming dim because it happens so slow. When you realize it you start to wonder if you need new, brighter headlight bulbs. Really you need to just need to clear up the plastic headlights.
There are a lot of different ways to clean up the lenses of your headlights. Toothpaste, Baking Soda, Vinegar, WD-40, Coco Cola, and Plastic Polish are just a few different things people use. Interesting thing is none of them last but more than a few weeks. To really repair the headlights the damaged plastic needs to be sanded off and a new UV resistant coating needs to be installed.
We use a 5 step process when restoring headlights to like new condition. It is three dry sanding steps to remove the damaged plastic from the lens. Then we follow it with wet sanding the lens to smooth the plastic down but still provide a slightly rough surface. For the last step we coat it with a UV resistant coating spray so the plastic doesn't turn yellow. Most kits have you polish the headlight with plastic polish after the the dry sanding. If you do this the damaged yellow plastic will not come through in just a few weeks. This is what allows us to put a Five year warranty on our headlight restorations.
There are a few companies out there that sell kits like the ones we use. If you purchase one of these DIY kits that comes with a UV resistant coating we have some tips to help you do it right the first time. First don't do the headlight restoration on a humid day. The humidity effects the UV spray and can make it cloudy. Make sure everything is taped off well because the spray will get on everything on the area that is not covered. Spray the coating from around 6 inches away and move at a pace where you are moving a little faster than on inch a minute. Lastly using a heat gun or hair dryer can speed up and help cure the UV coating so it does not get dirt or bugs in it.