Now that summer is in full swing around the country; you may have gone to cut on your Ford Bronco’s (whoever has one of those) AC for the first time since last summer, and instead of feeling a manufactured cool breeze on your face, you were met with a locker room-esq stink that nearly burned off your eyebrows. What is this smelly AC problem, and how do you fix the musty air conditioning smell? 

Why does my air conditioner smell bad? 

This has to be one of the more upsetting car problems. What really makes this problem so brutal is that the air conditioner will typically keep working just fine, but driving is tough to do when your eyes are watering from the foot stink blowing in your face. What could possibly make this musty air conditioning smell? 

“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.” 

Luckily, this air conditioner smell is easy to fix

Like a sweaty glass of cold water on a hot day, your car’s air conditioner makes condensation, and that liquid has to go somewhere. If it has nowhere to go, it gets funky and turns ugly fast. Air conditioners have a drain that allows this condensation to drip below the car. If you pay attention in the summer, you’ll likely see water puddles underneath your car after running the AC for a while. 

Although it’s meant to all escape via this drain, a little water can sometimes collect in the evaporator and get stuck there. This water begins to grow mold and bacteria, and then your air conditioner smells like a high school locker room. Aside from the horrible stink, this is also not the healthiest air to breathe. If this smell starts, it’s important to get it taken care of quickly. 

How do you fix a car’s smelly air conditioner? 

Consumer Reports suggests that you roll your windows down and cut on the interior fan (not AC) on low. You’ll also need some disinfectant spray like Lysol or another AC disinfectant and spray it into the plenum. 

The plenum is a box connected to your car’s HVAC system. The intake is usually found near the base of your windshield, where the wipers are located. You’ll see two small vents there, and that is where the plenum is and where your AC sucks air to cool and pump into the cabin. Spray your disinfectant into these vents liberally. The fan will then suck the spray through the system, killing the stinky bacteria. 

If you have a cabin air filter, this would be a good time to check if that needs cleaning or replacing. The cabin air filter is typically located behind the glove box. Either way, take the filter out before spraying to allow the spray to more easily move through the system. The better the flow of disinfectant, the more of the musty air conditioning smell it’ll kill. 

Once you have successfully fixed your car’s musty air conditioner smell, remember to run just your fan from time to time, especially once the weather cools down, to dry that excess condensation, keeping the smelly bacteria at bay.