If there is an odd, moldy smell that kicks in as soon as you turn your air conditioning on, you don’t have to close your nose and bear it. More likely than not, you’ve built up some mold and mildew thanks to moisture in your AC system. This moisture occurs naturally, and is part of the car, but if left for too long it can create mold. As air pumps past the evaporator and into the car, it picks up mold spores, which feed on the moisture. Luckily, they are easy to clean, and your car will smell good as new.
Note: This article deals with AC odors, which are moldy, mildewy smells (like old socks, wet dogs, etc.) For burning or chemically smells, take your car to a dealer immediately.
READ ALSO: HOW TO FIX A CAR THAT DOESN’T START
Removing AC Odors
Purchase a mold and mildew fighting disinfectant aerosol spray, such as a specialty duct cleaner. Specialty sprays may be the best bet for serious odors, but for smaller problems (or to stay ahead of potential smells) you can use an over-the-counter disinfectant spray like Lysol.
Alternatively, make your own all-natural spray with a vinegar and water. Mix up one part white vinegar with three parts water, then put it in an old spray bottle or solvent sprayer. While vinegar isn’t the most pleasant smell, it will fight the mildew naturally and it will fade off quickly.
Throw in the juice from half a lemon to get a slightly fresher and longer lasting scent.
Turn the car, fan, and the AC all the way off. Flick both switches into the off position and make sure the car isn’t running.
Spray your disinfectant into every single vent. Make sure you get in the backseats and hit the vents at your feet, which often pump the most air. There are also vents on the dashboard, and usually one on the pointing on the back windshield as well.
Keep the doors closed as you do this. You want the cleaning fluid to get in the system.
Turn the car on and the AC to max power, full blasting fan. This will start to circulate air around the system for you, getting your cleaning solution around the AC system. Keep it on this “Max” setting at first to kick the system into gear.
Find your re-circulation vent and spray into it generously, with the AC still running. You can find your re-circulation vent by checking your manual. It is often on the drivers side floor, near the console, or in the trunk. The little button with arrows pointing a circle tells your car to stop taking air from the outside, and instead recycle the air from the inside. Press this button if you have it, then spray down this vent to make sure your cleaning fluid is staying in the system.
Switch the AC from “max” to full fan mode. You want to be blowing more air, not cooling more air. This should prevent additional moisture from coming in.
For serious issues, lift the hood, replace the cabin air filter and spray down all the intake lines. If you have nasty odors coming from the car and no way to stop them, grab your owner’s manual and lift the hood. The AC system is back towards the windshield, under the plastic grate and filter where (different models have different methods — you must check your manual), and remove the filter, cleaning and replacing when necessary.
While there, spray the whole apparatus down with your cleaning aerosol to fight and kill any mold or mildew.
Run the car, doors open, with the AC off and the fans on full for five minutes. This is your final “drying out,” and it will prevent mold and mildew from reestablishing your old odors.
Take the car to your dealer if the smell persists. If the smell still won’t go away, don’t ignore it. It won’t get any better on its own. Take it to the dealer to make sure the smell is not the cause of something more serious, and to handle the problem before it becomes worse than just a bad smell.
Preventing AC Odors
Turn off your AC 4-5 minutes before stopping the car. This gives the evaporator time to dry off excess moisture (key for mildew/mold growth) using the hot air from the engine. No moisture means no mold, which means no smell!
Keep the fans on high as the car shuts down. With the AC off, keep the fans blasting to make sure a lot of air hits the evaporator and removes any mildew, moisture, or mold spores from taking root.
Note — this is a way to prevent further growth. It will likely not help remove the actual smell if it is already there.
Blast the fans on high, doors open, once a year on a hot, dry day. This can prevent all mold from ever getting a foothold. Remember that the AC, not the fan, creates the moisture that spawns mold. The fan will just heat it up from the hot car motor (hopefully killing it) and then remove it from the AC evaporator.
Spray down the ducts with disinfectant every 3-6 months if you live in a hot humid area. Warm, wet environments are paradise for mold and mildew. Furthermore, the more you use your AC, the more likely it is to grow dirty. Keep on top of the issue with regular cleanings, as noted above.