How to Get Rid of the Musty Smell in Your Car's Air Conditioning

It's a pretty easy fix.

By Devin Pratt

Few things are as nice as a car's air conditioning on a hot summer day. But what to do when the air coming out of the vents smells like a sweaty sock?

"What you're probably smelling is condensation coming from the evaporator inside the heating and cooling system," says Jake Fisher, Consumer Reports' senior director of automotive testing. “Basically, water collects in that area and if it sits long enough, it creates the musty smell,” he adds.

Most of the water should leave your car through the evaporator drain under the underbody of the vehicle. “You've probably seen a small puddle of water under the bottom of your car on a hot, humid day,” Fisher explains. But sometimes, some of it accumulates on the evaporator, and if it stays there for a while, bacteria and mold will grow and it will even smell in the cabin of the car. But there is a fairly easy solution.

First, turn on the car's interior fan on low setting and open the car windows. Get a disinfectant like Lysol or some type of AC disinfectant product from an auto parts store and spray it in the area called the plenum.

The plenum is a box that connects to the HVAC system (heating, ventilation, and air conditioning system), and can be found at the base of your windshield at the height of the windshield wipers. Right there you will see some vents that are the plenum of your car. That's where the air coming into your heating and cooling system comes from.

It liberally sprays the cleaner on both sides of the plenum intake vent and is drawn into the system by the fans themselves, where it will kill bacteria and help eliminate musty odors. At that time it is preferable to keep the windows open to help ventilate the car. If you have a cabin filter, remove it before spraying the sanitizer to help it move through the system. It could also be a good time to change it, because a dirty filter prevents optimal airflow. Cabin filters are usually quite easy to reach, often located behind the glove box door.

To keep your vents in good condition during the summer, turn off the air conditioning and let the fans run for a few minutes before turning off the car's engine. This will help remove some of the moisture that forms on the air conditioning vents.

Editor's note: this article has been adapted from an episode of Talking Cars.

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Consumer Reports has no financial relationship with the advertisers on this site. Consumer Reports is an independent, nonprofit organization that works with consumers to create a fair, safe, and healthy world. CR does not endorse products or services and does not accept advertising. Copyright © 2023, Consumer Reports, Inc.