How To Stop Condensation in Your Car

February 10, 2017

window foggingYou’re already running five minutes late for work, so you dash out the door, hop in the car — and realize you can’t see. At all. Your windshield and windows are fogged with moisture. Lacking a squeegee, you swipe at the windows with your sleeve. Window fogging is definitely not a great start to the day.

Here’s the good news: window condensation in cars isn’t something you just have to accept. There are a few ways to prevent window fogging, so on the next damp morning, you won’t be late for work.

What causes condensation in cars?

Condensation happens when there’s a difference between the temperature and moisture levels inside and outside the car. When warm, humid air meets cold glass, water from the air condenses on the glass, forming water droplets or fog.

When your car windows fog on the outside, that means the surrounding air is warmer than the glass. For instance, if you’re speeding through a muggy summer night with the air conditioner blasting, your windshield may get cold enough for water droplets to condense.

When you see condensation inside car windows, that signifies moisture inside your car. Often in the winter, the interior of your car is damper and warmer than the air outside, so water clings to the inside of the glass. Even breathing may be enough to steam up the glass.

How to fix window fogging

condensation inside windowFirst, let’s talk prevention. If you often see condensation inside the car windows, the main problem is moisture in your car. Make sure you’re not leaving sweaty gym clothes (eww), damp towels, or other moisture sources inside overnight. Older cars may have faulty gaskets or small leaks that allow rain into the car. To remove moisture, you can buy a car dehumidifier, which is a bag filled with silica. Or, for a super-cheap solution, fill the foot of some tights with cat litter, knot it and stow it under the seat.

Another way to prevent condensation inside windows is to keep them clean. Water droplets coalesce around tiny particles of dirt, so a thoroughly cleaned window gives them fewer opportunities to condense.

What if you’re driving and you start to see condensation inside the windshield? Here’s a solution: run the air conditioner, the heater and the defroster simultaneously. It may sound crazy, but it works. As one physicist explains: “The air conditioner dehumidifies air because water condenses inside it when the air goes past the cold tubes with the refrigerant inside. Heating it up way past its dew point makes it feel dry, and it is dry — it’ll help evaporate any condensation that’s on the windshield — and even more quickly the hotter it is because heat is needed to cause the liquid water to change phase to a gas.” Got all that?

Now, if your main problem is window fogging on the outside, there’s not much you can do. Use windshield wipers and the defroster for the windshield, and carry a squeegee or rags in your car for the windows.

How to get condensation out of headlights

condensation in headlightFoggy windows are an easy fix — foggy headlights, not so much. While a little early-morning dew is OK, persistent condensation in your headlights can be a safety hazard. And in some states, a vehicle with fogged headlights may not pass inspection.

NAPA Auto Parts has a handy guide to fixing condensation in a headlight.

  • Step 1: Get out your toolbox and your car manual, and carefully remove the affected headlights.
  • Step 2: Remove bulbs, plugs and vents, but don’t break the seal between the lens and the housing.
  • And Step 3: Dry out the headlight assembly using a hairdryer, silica gel packs or even an oven (on low, low heat, unless you want a puddle of plastic)

Then, NAPA advises, inspect everything to see if you can find out where water is getting in. Silicone can fix cracks or malfunctioning seals. Clean the headlight vents with air, and watch out for creepy-crawlies: “Spiders are notorious for building their nests in the darnedest of places, and headlight vents seem to be one of their favorites.” Aaahhh! has lots more tips for car owners to keep your vehicle running. We also have the best way to save money on car insurance: Enter your information once and get multiple free quotes from great insurers. Try it now!

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