Automakers used to manufacture headlight lenses from glass. The bad thing is that glass limits a lens' shape and size so the OEMs switched to a more aerodynamically friendly and lighter material-plastic. Plastics and polycarbonates don't just weigh less than glass, they're also cheaper, but the biggest advantage they have over glass is that they can be molded into just about any shape or size you can think of.
Of course, with advantages come disadvantages. Plastics and polycarbonates are porous materials that expand with heat. The heat from the bulbs and sunlight exposure creates pores that allow road debris to embed into the plastic. All of this debris, along with the sun's rays and car-care chemicals, can turn an otherwise good set of headlights into cloudy, yellow-hazed, plastic eyesores. But don't replace those expensive headlights just yet; keep costs down and restore them yourself. All you really need to do is remove that top layer of oxidized plastic for a new looking set of lenses.
Here's The Trick:
BUY OR BORROW:
One bucket of water
Step 1: Pop your hood and clean any dirt and debris from the headlight and its surrounding area. Mask off the headlight assembly with tape to avoid scratching the paint while wet-sanding.
Step 2: Soak a piece of 600-grit sandpaper in a full bucket of water and thoroughly dampen the headlight lens. Wet-sanding is less abrasive and allows you to see the results easier. Sand the headlight for about 10 minutes using side-to-side strokes. Be sure the sandpaper is always wet and don't worry if the lens begins to look worse than when you started.
Step 3: Wipe off any residue from the lens and repeat the process with 1,000-grit sandpaper using the same procedure as above. Keep it up until the lens begins to appear less cloudy.
Step 4: Wipe off the lens again and switch to 2,000-grit sandpaper. Be sure the lens and the paper are thoroughly wet. This step requires patience so don't rush it. Sand the lens evenly for a good 20 minutes and keep things wet. You're done when the lens looks new and clear.
Step 5: Dry things off with a towel and prepare for discouragement. Once wet-sanded and dry, the lens is bound to look a bit worse than when you started. This is due to the millions of scratches that even the finest grit sandpaper can't get rid of. Use an abrasive rubbing compound to remove them. If you use an electric buffer, be sure to not burn the plastic.
Step 6: Remove the tape, apply a coat of wax over the lens, and view the magic. Re-apply wax every few months for further protection against future damage.