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Condensation can cause moisture to build up inside your car. It’s something you shouldn’t overlook because moisture can lead to visibility issues, especially if there’s condensation in the windshield or any of the other glass. Mold and mildew are also not uncommon if you don’t take care of the problem immediately.

Before discussing solutions, let’s understand what causes the issue.

Why Is There Condensation Inside My Car?

Condensation happens when warm air containing moisture touches cold surfaces like your car’s windshield and windows. It usually occurs when the temperature inside your car is significantly different from the temperature outside.

While some condensation is normal due to moisture in the air, high humidity can cause the moisture to be worse. But extremely heavy condensation can mean there’s a leak allowing water to enter the vehicle.

image of a 2001 mercury marquis grommet
This grommet wasn’t seated during the installation of a new hood release cable on a 2001 Mercury Marquis, and the first time it rained after the work was done, water entered the car at this point. Grommets like this and wire harness grommets can cause water to enter. | Image Source: Richard McCuistian
, What Causes Condensation In a Car?

Pro Tips are nuggets of information direct from ASE-certified automobile technicians working with CarParts.com, which may include unique, personal insights based on their years of experience working in the automotive industry. These can help you make more informed decisions about your car.

Pro Tip: Sometimes water can enter the vehicle along the base of the windshield or through a poorly sealed body panel seam. Some 2000s Ford pickups may have water to enter around the high mount stop lamp at the top of the back of the cab.

Here are some factors that can contribute to moisture buildup inside your car: 

Clogged A/C Evaporator Drain

If the evaporator drain on the A/C is clogged with leaves or other debris, water can enter the vehicle due to an overflowing evaporator case from normal condensation on the condenser.

Wet Carpets or Floor Mats

It’s not uncommon to get in your car even when your shoes are wet, especially on rainy days. Unfortunately, your carpets or floormats could absorb the moisture on your shoes, which could then condense on your ride’s interior surfaces.

Damaged Door Seals

Seals or weatherstripping create a waterproof barrier between your ride’s interior and exterior. They prevent water and other elements from entering your interior—at least until they wear out or get damaged as your ride racks up mileage.

Because door seals are typically made of rubber, they can lose their flexibility over time. You can check the condition of your weatherstripping by squeezing them between your fingers. If they spring back, they’re still in good condition. Otherwise, it’s time to have your doors repaired.

Leaky Sunroof

A blocked water drain in your sunroof mechanism can cause leaks, allowing water to enter your interior when it’s raining.

Sunroof leaks aren’t always that obvious. Sometimes, water can get in through your car’s headliner and pillar panels. It’s hard to notice it until you step on a wet floor mat or notice moisture in your car seats.

If you suspect that your sunroof is leaking, don’t think twice about taking your car to a professional. Besides condensation, leaks can damage your interior in the long run.

Old Cups of Coffee or Open Water Bottles

Leaving your old cup of coffee or open water bottle in your car can contribute to condensation inside your car. Over time, these containers can release moisture that can condense on your window glass and windshield.  So don’t leave coffee cups and water bottles inside your car for a long time. 

Bad Heater Core

Although there are a lot of unalarming reasons why condensation happens in your car, there’s one that’ll give you a headache. A bad heater core can cause condensation in your car.

A heater core is a radiator-like component that helps warm your car’s interior. Once there’s a leak in the heater core, warm coolant can enter the cabin, creating condensation.

A sign that a bad heater core is the culprit is when the window glass will feel greasy. You might also notice a sweet smell throughout the interior, indicating that coolant is leaking out.

How to Prevent Condensation In a Car

man cleaning car interior to avoid moisture
Anything wet inside your car can contribute to condensation, so make sure to keep your interior clean and dry.

Although condensation occurs naturally, there are ways to prevent it. Here are some of the ways to avoid having too much moisture inside your car:

Keep Your Interior Dry

Anything wet inside your car can contribute to condensation, so make sure to keep your interior clean and dry. You can manually check if there’s moisture in your car’s upholstery.

Don’t forget to inspect your floor mats and carpets regularly. If your mats are wet, you can remove and dry them. This might also be a good time to clean your vehicle and get rid of any crumbs of dirt.

Use Your A/C

Your car’s a/c system stabilizes the temperature inside your cabin, helping remove humidity inside your vehicle. You can activate your A/C fan or blower to help remove moist air from your car.

Turn off Your A/C Recirculation Valve

Use the A/C recirculation valve only when it’s needed. An A/C recirculation valve allows the same air to recirculate inside the cabin instead of introducing outside air. It’s helpful in maintaining a constant temperature, especially when it’s humid outside.

However, recirculating the same air in your car can cause moisture to stay inside your cabin. You can turn off your A/C recirculation valve to get new dry air from the outside.

Park In a Covered Area

If you often notice condensation in your car when parked, re-evaluate where you’re parking your car. To avoid condensation, it’s always a good idea to park in a covered area to keep the temperature inside your car more consistent.

Buy a Moisture Absorber or Dehumidifier

You can also shop for moisture absorbers and portable dehumidifiers online. Moisture absorbers can absorb and remove bad odor, so you can keep your interior smelling good.

A portable dehumidifier can also take out moisture in the air. Simply place the device inside your vehicle and close your doors and windows.

Use Baking Soda

If you don’t like to spend money on aftermarket moisture absorbers, you can use baking soda as a natural moisture absorber. Simply open a box of baking soda and place it inside your car.

Make sure to close all the doors and windows. Baking soda can absorb moisture and unwanted odor, so it works just like a commercial moisture absorber.

Leave Your Windows Open On Sunny Days

If you can, open your windows when it’s sunny. This will allow the warm air from the outside to enter your ride’s interior and reduce its moisture. Just make sure to roll the windows back up when you park your car.

About The Authors
Written By Automotive and Tech Writers

The CarParts.com Research Team is composed of experienced automotive and tech writers working with (ASE)-certified automobile technicians and automotive journalists to bring up-to-date, helpful information to car owners in the US. Guided by CarParts.com's thorough editorial process, our team strives to produce guides and resources DIYers and casual car owners can trust.

Reviewed By Technical Reviewer at CarParts.com

Richard McCuistian has worked for nearly 50 years in the automotive field as a professional technician, an instructor, and a freelance automotive writer for Motor Age, ACtion magazine, Power Stroke Registry, and others. Richard is ASE certified for more than 30 years in 10 categories, including L1 Advanced Engine Performance and Light Vehicle Diesel.

Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic. The accuracy and timeliness of the information may change from the time of publication.

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