Why Do Headlights Turn Yellow? (Not What You Think)

Your headlights need to be able to light up your surroundings as clearly as possible, but this is something that’s hindered when their lenses become yellow over time.

So, if you notice a yellowing on your headlights and you don’t know how to proceed, keep reading this article to see what I found out!

Why Do Headlights Turn Yellow?

Your headlights will turn yellow due to oxidation on the surface of the lenses. Polycarbonate lenses are more common because they’re more durable than glass, but this material reacts more with the air and this is what makes them change color. They might also get yellowed due to the buildup of dirt and chemicals.

Keep reading to learn everything you need to know about why your headlights turn yellow over time, including a deeper dive into the reason, how to deal with and prevent it and more useful facts and tips!

Why Do Plastic Headlights Turn Yellow?

If your plastic or acrylic headlights turn yellow, it’s most likely because they’ve oxidized from prolonged exposure to ultraviolet light.

Plastic reacts with UV rays more readily than glass, which is why it’s less common on older cars that don’t have polycarbonate headlight lenses.

Most manufacturers switched to this material because it’s cheaper than glass, but it came at the cost of yellowing over time.

While manufacturers often include a protective film over the lenses to shield them from these rays, this method becomes less effective over time.

However, since most UV light we come in contact with is from the sun, this is less of an issue for vehicles that are normally parked in shaded areas or are almost always driven at night.

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Aside from this, their color might also change due to dirt and other chemicals building up on the lens for some time.

Having the lenses made of plastic as opposed to glass means they’re more permeable, so these substances can also get inside the housing.

This route to yellowing is less common and highly dependent on the type of chemicals your car is exposed to, but it does happen nonetheless.

Overall, both of these ways through which plastic headlights turn yellow make it difficult to clean them using the usual methods and agents.

Do Glass Headlights Turn Yellow?

Do Glass Headlights Turn Yellow?

Glass headlights do not turn yellow because the material doesn’t react on contact with UV light to undergo oxidation.

In the rare event that your glass headlights do turn yellow, it’s probably the result of dirt and other chemicals building up on the surface.

That being said, glass is a lot less permeable than acrylic, meaning there are less avenues through which dirt and other chemicals can get underneath the headlight housing even if you allow them to gather on the surface for long.

This means that if yellowing occurs through buildup, it’s a lot easier to clean out like you would a normal window.

How Do I Stop My Headlights from Turning Yellow?

You can keep your headlights from going yellow (or at least slow down the process) if you understand the causes detailed in the previous sections.

Yellowing from contact with UV light is going to be difficult to stop if you’re regularly driving during the day, but it can be delayed significantly.

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One main method of avoiding a yellow headlight is to refrain from parking your car in direct sunlight. If you’re at home, leave it in the garage, and if you’re at work, consider underground parking if you have the option.

If none of these are available to you, try and find a way to park the car in such a way that the headlights are facing away from the sun.

You can also look into getting a film for the headlights that protects them from UV light if the original one has worn down. Keep the protection fresh by swapping it out every few weeks if your car is out in the sun often.

Other yellowing agents can be addressed early through general washing and maintenance of your headlights.

Whenever you’re washing your car, pay special attention to the headlights. Use warm soapy water, a sponge and a soft lint-free fabric to dry the lenses when you’re done.

Apart from the usual cleaning processes, you can also make time to polish the headlights in order to catch yellowing before it gets out of hand.

Can Yellow Headlights Be Restored?

Can Yellow Headlights Be Restored?

Yellow headlights can be restored because the yellowing usually shows up first on the protective film used to keep UV light at bay.

If the film is gone, you can still get rid of the yellowing because it occurs by layers. If you get rid of the affected layers, you can get your headlights back to normal.

Does WD-40 Clean Yellow Headlights?

WD40 will restore your headlights, but it’s a very short-term solution. If you’re lucky, it’s going to last 2 weeks before the lenses revert to their original condition.

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Because the initial results look very impressive, it’s a trick used by people selling used cars to make them appear more appealing because it hides the problem long enough to lure buyers in.

How Do I Get Rid of Yellowing Headlights?

As stated above, you can get rid of yellowing headlights by targeting the oxidized layer(s), as the effect is largely only surface level.

To do this, start by washing the headlights with warm water, soap and a sponge before wiping it dry using a soft microfiber cloth.

Afterward, use very fine sandpaper to buff out the yellow. This will get rid of the yellowing, but the lenses are going to look blurry, so use polish to buff them out and get them clear again.

Finally, apply a new coating to protect the headlights from direct sunlight and repeat the process every few months as needed.

To know more, you can also check our posts about how long do headlights last, if toothpaste cleans headlights, and how long do LED headlights last.

Conclusion

Yellowing headlights are primarily caused by direct contact with ultraviolet light from the sun, which occurs more on plastic than glass lenses. You can prevent yellowing by not leaving your car parked out in direct sunlight for long.

If your headlights get yellow over time, you can restore them by targeting the impacted layers through a combination of washing, sanding and polishing.

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