What Causes Foggy Headlights (and How Can You Fix It)? – Jalopnik

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Whether you’re reading this because you’re a registered gearhead and would like to learn more about wrenching, or because you Googled “why are my headlights yellow,” you can probably learn more about foggy headlights. Especially if you’re like so many of us nerds who own older cars. Yellow, foggy headlights look terrible and can drastically age the appearance of a car, no matter how nice everything else looks. However, if you repair them and restore your headlights to their original transparency, your car will come back to life.

It’s not just about looks either. Foggy headlights are dangerous because they limit the distance your headlights can illuminate, reducing forward visibility at night. They even reduce the ability of other cars to see you at night. So if your lights are looking worn and old, let’s take a look at why this is happening and how to fix them so you can avoid this in the future.

Oxidation. That’s the short answer. Most modern headlights are made of polycarbonate and are factory fitted with a protective ultraviolet (UV) sealant layer. Over time, that clear coat wears off; the sun, debris and road salt in winter can all play a role in wearing down the protective coating. Once it’s gone, the sun’s UV rays will start to damage polycarbonate headlights through oxidation.

This can and will happen over time with most plastic headlights, but it can be exacerbated by other external factors. If you use harsher soaps to clean your car, they can damage the clear coat and speed up the oxidation process. Persistent high temperatures can also make it worse, so if you live somewhere in Arizona where summer daytime temperatures are nearly uninhabitable, your headlights may suffer. Or if you live in an area where winters are harsh and road salt regularly lands on the face of your car, you can expect more rapid headlight fogging.

Cloudy headlights are no joke either. In a 2018 study AAA said cloudy headlights can reduce brightness by 80%, which is incredibly dangerous. And it doesn’t just happen to old cars. According to that same AAA study, depending on outdoor conditions, headlights can turn yellow and fog up within three to five years.

So cloudy lights are not only ugly and make people not want to be friends with you (okay, maybe that part is just in my head), but they are also dangerous. Fortunately, it is relatively easy to fix, if done correctly.

Let’s start with what not to do. Do not use acetone. Although acetone is great for cleaning glass, cars haven’t used glass headlights in decades. Acetone is a strong solvent and damages the plastic, which has unpleasant consequences in the long term. While it may look good right away, the damage it causes to the headlight is not worth it in the long run. The same goes for bug spray, as DEET will damage the plastic in the same way. Some DIY hacks like baking soda aren’t bad. Toothpaste also works; they are both abrasive enough to get the job done.

However, the best methods are a polish and good old-fashioned elbow grease. You can polish your headlights in several ways, for example by purchasing a headlight restoration kit 3M’s Ultra Headlight Restoration Kitusing a traditional polishing compound and an orbital polisher, or even wet sanding with fine sandpaper. Essentially, you want to polish the headlights to remove surface level oxidation.

However, this is the most important thing: you need to seal the headlights afterwards. Regardless of how you polish the restoration, your headlights will lose their protective clear coat, which will simply cause them to oxidize again, but this time even faster. To prevent this, a new protective layer is necessary. There are numerous products that can be used for such protection, such as paint protection film or Cerakote or other ceramic coatings. Both types of protection can be applied by yourself or by a professional.