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Moisture in Headlights Doesn’t Have to Mean It’s Time for Replacement

A close-up on a car headlight with moisture inside the housing.

Moisture in headlights can be a frustrating problem to deal with. Not only does that fogginess affect the amount of light the unit projects, but it can also cause corrosion over time inside the assembly. How does moisture get in there, and what can you do about it? Check out these tips for dealing with a foggy headlight.

Ventilation = Condensation

Moisture in headlights is quite simply a matter of science at work. Since most headlights generate heat, they need to be ventilated, which means that they feature small vents that can suck in moisture when the car is turned off. If the outer lens cools more quickly than the air inside the headlight unit, it can cause condensation. This explains why you most often encounter condensation in the morning after your car has been parked overnight. Sometimes, a crack in the housing itself or bad headlight seals can also allow moisture to creep in.

What Can You Do About It?

Foggy headlights

Usually, when you turn the headlights on, the heat causes the moisture to evaporate. It can also evaporate on its own over the course of the day, as the sun warms things up enough to do the same job. Driving the car can also help, as it allows air to pass through the vents in the light housing and clear out the moisture, much like running the defroster in your car’s cabin clears the windshield.

It’s worth checking to make sure that your headlight vents aren’t blocked, as this can lead to persistent moisture and fogging issues. Insects, road debris and spider webs can all block vents. You might also want to consider spraying compressed air through the vents in order to help clear the moisture more quickly.

Is It Time for a Replacement?

If you’re seeing more than a normal amount of moisture in your headlights, or if you’ve noticed more water inside the housing after a rain storm, you could be dealing with a cracked headlight or a problem with the rubber gaskets that seal it to the body. Most of the time, gaskets can be replaced individually, but if the headlight housing is cracked, then you’ll most likely have to replace the entire unit.

Follow these steps to determine just how far gone your headlights are — and don’t automatically assume that, just because you see some moisture, it’s time for a new set.

Check out all the lighting parts available on NAPA Online or trust one of our 17,000 NAPA AutoCare locations for routine maintenance and repairs. For more information on dealing with moisture in headlights, chat with a knowledgeable expert at your local NAPA AUTO PARTS store.

Photo courtesy of Flickr.


Benjamin Hunting View All

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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