An SUV's headlights at night. Some headlights lose their ability to light the road ahead as they age. Here's how to deal with fading headlights.

Do Headlights Dim Over Time? Here’s How to Deal With Less Light

Do headlights dim over time? It’s a question you may have asked yourself one evening while traveling along a darker-than-usual back road in your vehicle, not entirely convinced that your headlights are giving it their all in terms of illuminating the path ahead.

The answer is “yes,” but it’s not always easy to tell just how far gone your own lights are due to how gradual the process can be. What’s more, the reasons headlights get dimmer are varied, with different solutions available to try and rectify the problem.

Let’s take a look at dimming headlights and what you can do to get back to having bright lights.

Old Bulbs, Bad Bulbs

Although LED and HID headlights are becoming more common, the majority of cars and trucks still make use of halogen bulbs as their primary light source. In theory, halogen lights are designed to retain almost 100 percent of their initial brightness over time due to how tungsten particles in the filament are recycled during the illumination process.

In reality, however, there can be many factors affecting how well a halogen bulb illuminates as it ages, including inefficiencies in power usage, design flaws that pull too much power initially to appear brighter out of the box (prematurely wearing out the bulb) or loose filaments that can make it harder to focus the light.

In this case, a replacement bulb is your best bet — and to choose a high-quality bulb when doing so. Always remember to replace headlight bulbs in pairs, too, to guarantee even lighting.

Hazy Days

Another common reason for the question “do headlights dim over time” is the headlight casing itself becoming hazed or occluded. There are several reasons as to why headlight lenses, which are almost always made out of plastic, can cloud to the point where they begin to block light.

Headlights in the snow and wet

Heat is sometimes the culprit, and although halogen bulbs rarely generate enough to blacken the inside of a lens some older headlight designs can cause this problem. In this case, a replacement lens is the only viable solution.

More often, however, you’ll discover that the haze is on the outside of the headlight cover, and is caused by environmental factors. Ultraviolet light from the sun is the leading culprit, followed by road salt and grime that interact with the plastic and cause it to lose its transparency. In these cases, a simple lens polish kit that uses a mild abrasive to remove the outer layer of discoloration can work wonders for brightening your headlights.

Headlights that fade over time are impossible to avoid, as it’s a part of how the components wear out, but it’s essential that you do something about it. By replacing the bulbs, installing new headlight lenses or getting new bulbs, you can ensure you’ll have a clear view of the road ahead.

Check out all the vision and safety products available on NAPA Online or trust one of our 17,000 NAPA AutoCare locations for routine maintenance and repairs. For more information on how to deal with fading headlights, chat with a knowledgeable expert at your local NAPA AUTO PARTS store.

Photo courtesy of Creative Commons.

about author

Benjamin Hunting

Having been bitten by the car bug at a young age, I spent my formative years surrounded by Studebakers at car shows across Quebec and the northeastern United States. Over ten years of racing, restoring, and obsessing over automobiles lead me to balance science writing and automotive journalism full time.  I currently contribute as an editor to several online and print automotive publications, and I also write and consult for the pharmaceutical and medical device industry.

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