How to Get Rid of the Musty Smell From Your Car’s Air Conditioner

Car air conditioner Photo: istock

Few things are as welcoming as a car’s AC on a steamy summer day. But what do you do when the air coming out of your vents smells like a sweaty sock?

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

Most of the water is meant to exit your car via the evaporator drain under the bottom of the vehicle. You’ve probably seen a small puddle of water under the bottom of your car on a hot, humid day, says Fisher. But sometimes, some of it collects in the evaporator, and if it sits in there for a while, bacteria and mold are going to form and you’re going to smell it in the cabin of the car. Fortunately, it’s actually a pretty easy fix.

First, turn on the car’s interior fan on the low setting and open up the car’s windows. Get a disinfectant like Lysol or some kind of AC disinfectant from the auto parts store and spray it into what’s called the plenum.

The plenum is a box that connects to your HVAC system, and the intake can be found at the base of your windshield where your wipers are located. You will see vents there, and that’s the plenum. That’s where the air comes from that goes into your heating and cooling system.

Spray the cleaner liberally into both sides of the plenum intake vent, and the fans will pull it into the system, where it will kill the bacteria and help get rid of that musty odor. You’ll want to keep your windows open to help air out the car. If you have a cabin filter, remove that before you spray the disinfectant to help it move through the system. It might be a good time to change it, too, because a dirty filter can prevent optimal airflow. Cabin filters are usually pretty easy to get to, often mounted behind the glove compartment door.  

To help maintain your vents in the summer, turn off the air conditioner and let the fans run for a few minutes before turning off the car’s ignition. This will help clear out some of the moisture that forms in the AC vents.

This article has been adapted from an episode of Talking Cars.