What to Do If Your Car AC or Heater Smells

Sun Devil Auto Expert, published on 02/29/2016

If you’ve ever fired up your car and been hit with a nasty smell coming from the vents, you’re not alone. Before you can figure out how to get rid of the odor, you need to know what is causing the smell in the first place. So, what does it smell like?

Dank and Musty

Fungus, mold and bacteria thrive in small, moist, enclosed spaces like your vehicle’s cooling system. If the odor coming from the vents smells like a gym locker, this is probably the cause. One way to combat this is to turn your air conditioner off at least five minutes before turning off the vehicle and letting the fan run to help dry up residual moisture. You can also purchase anti-bacterial products that can be applied directly to the air conditioner case and into the vent system to kill current growth and prevent it in the future.

Dusty and Dirty

Air filters collect dust mites, dirt and pollutants, the buildup of which can cause an unpleasant smell from your vents when you use the AC or the heater. This putrid smell can be avoided by replacing air filters every 10,000 to 15,000 miles as recommended by the vehicle manufacturer. If you have a reusable filter, be sure to clean it every few months.

Sickly Sweet

This is the smell of anti-freeze which is a highly toxic substance. If a sweet smell is emanating from your vents, you should see a technician immediately to locate and repair the leak.

Fuel Smell

The smell of gasoline is usually an indication of a fuel leak. When you turn on the air conditioner or heater, the fumes, along with the smell, are sucked up and blown right into the cabin of the vehicle. As with exhaust fumes, the inhalation of gas fumes can be hazardous. It’s important to have your fuel system checked out by a mechanic as soon as possible, if you smell fuel coming from your vents. 

Rotten Eggs

Unfortunately, this smell generally means that something is decomposing. Animals often find refuge in vehicles, seeking warmth or shelter within a vehicle’s engine area. (Knocking on the hood of your vehicle before starting it, especially if you park your vehicle outside, is a good idea and may help scare off any creatures.) Animals crawl up in the underside of vehicles to nest and, while there, urinate, defecate and sometimes expire. In this case, the only options are to wait it out or to find and remove the dead critter.

The key to knowing what to do if your car AC or heater smells bad all depends on the cause. Once you’ve determined the source of the odor, eliminating it is a breeze.

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