Tech Tips
Getting the Yellow Out
Step-by-step restoration of hazy plastic headlights
by Matthew Crawford
Desert Stars Section
Modern cars all seem to suffer from a similar phenomenon when it comes to the ugly yellowing issue on their headlights. Ultraviolet rays are not nice to the compounds in our curved and stylish lamps. Replacement is pricey – but eventually unavoidable, in my opinion – as polishing kits are a temporary fix. As the cars come off the factory line, all headlights have a UV coating to help keep the plastic clear. In time, this coating begins to wear away, allowing the lenses to discolor. Sanding and polishing the headlights to remove the yellowing will remove the UV coating entirely. But if you want to maintain a clean look, not to mention retaining the safety aspects of clear headlamps, this restoration can make a great improvement.
1. My CLK was a good example of the problem. As you can see, the housing is yellow and hideous.
2. You want to protect the paint around the headlamp you are working on because you’ll be sanding the surface and you do not want to damage the car’s paint. One of the first things I do is pop the hood and tape around the lamp housing to protect the finish from the aggressive treatment on the lights. Raising the hood allows much more access to the top of the plastic housing. Normally I’d use blue painter’s tape, but I didn’t have any on hand. As I’m in the midst of a clay-bar, polish and seal project on the paint, any residue from the traditional masking tape will be removed shortly.
3. Once taped up, it is time to start with a 1,000-grit wet sanding. Get everything good and wet and keep it that way. You will want to spray the area as you work. Wet. Sand. Wet. Sand. Wet, etc.
4a. With the paper and the lamp wet, start sanding in one direction. I use the parallel lines in the lamp as a guide and first sand with them. You will start to get a thin yellow mud from the minute layers you are removing. Make sure to apply pressure evenly to the area so the surface removed is even around the lamp face.
4b. After you’ve sanded the entire surface well in one direction, change to a perpendicular angle. 4c. Remember to wet it continuously.
5. Now that you’ve done a thorough job in both directions, it’s time to rinse and hit it with 3,000-grit sandpaper. I usually do this in a circular motion, but going in opposite grains will also work. Continue sanding and wetting. All the yellow will wash away and the clarity should start returning to a haze. It won’t be clear until it’s polished.
6. Wipe the lamp down really well with a micro-fiber towel – now it’s time to polish!
7. For polishing, use Meguiar’s PlastX and a small buffer on a drill (I’ve had better luck with a plug-in drill than a cordless). Think of this step as a waxing process – a little goes a long way, but you want it all over the surface. Don’t goop it on or you’ll make a mess, but continue adding a small amount to the buffer so there is enough liquid applied to do the work.
8. Once you have a nice even haze, pull out a clean micro-fiber towel and buff away. You will be amazed at the improvement. It looks proper again.
9. I already had most of what I needed to do this job and my buffer is still in good shape. I just needed new sandpaper. 
10. If you don’t protect your headlights after treatment, yellowing will return within a week or so (my experience here in Arizona). For this, Meguiar’s offers a UV protection product to help save the life of the job you just performed.