Why Do Plastic Headlight Covers Go Cloudy?

| January 2, 2013

car plastic headlight cover Headlights are the eyes of a car. From the friendly round lights of the Fiat 500 to the angry ellipticals of the Dodge Viper, they give every car a distinct look and personality. But if you take a look at cars built in the 1990s and early 2000s, you might notice that their “eyes” have become dull and cloudy. Auto repair shops will gladly sell you replacement units, but a far cheaper alternative is to find a local auto parts store on the DexKnows website and pick up a restoration kit.

It’s not just aesthetics

Cloudy headlights let down the overall appearance of the car. It doesn’t matter how immaculate the paint is; if the “eyes” are foggy, the overall appearance is a little forlorn. And cloudy headlights aren’t just a cosmetic issue. They reduce the amount of light that can be thrown on the road ahead, limiting your ability to see at night or when it’s raining. That makes them a safety issue, too.

A new problem

Go back 30 years and this problem didn’t exist. That was because headlights were made from glass. Glass transmits light very well and is easy to clean but has two drawbacks in automotive applications: It’s not readily formed into the complex geometries demanded by car stylists, and it’s easily broken.

To get around these limitations, car manufacturers switched to a type of plastic called polycarbonate. Polycarbonate has great impact resistance, transmits light almost as well as glass, and can be readily formed into complex shapes. But it is easily scratched and, like most plastics, deteriorates when exposed to ultraviolet light (the same UV rays that let us tan).

To overcome these weaknesses, polycarbonate headlights are given a UV-resistant coating. This lasts for a number of years, but grit and dirt thrown up from the road, plus frequent washing and that darn UV light gradually wear it away, exposing the polycarbonate to the elements. Once this has happened, the light takes on that cloudy appearance.

Restoring cloudy headlights

Replacement headlights can cost upward of $500 each. Fortunately, a number of companies have launched restoration kits. In general, these consist of abrasive material to remove the outermost layer of the polycarbonate and any of the UV-protective coating that remains, plus a sealant to re-cover the newly cleaned surface.

Skepticism about these kits is only natural, but testing undertaken by Consumer Reports showed that they work. Results of testing carried out on kits from Sylvania3MTurtle Wax and Fast Brite were published in March 2012. The conclusion was that “all the headlight restoration kits worked to some degree on at least some headlights, but only the Sylvania could be used with all tested lenses.”

Cloudy no longer

If you want to brighten cloudy headlights (and it’s a good idea just from a safety perspective), pop down to your local auto parts store and pick up a kit. If you don’t know where the nearest one is located, the DexKnows local listings site does!

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Category: Auto Maintenance, Auto Parts, Auto Repair, Autos

About the Author ()

After twenty years in the automobile industry the craft of wordsmith called. Putting down the wrench, Nigel picked up a keyboard on which to express his passion for all things automotive.