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4 Foul Smells From Your AC (And How to Fix Them)

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Air conditioning climate control system symbols explained icon meaning car dashboard
Photo: The News Wheel

Spring has sprung, and before you know it, summer will be heating up. That means your favorite car feature will be the air conditioning. If you have not already checked that your AC is in working order, do it as soon as you can. If there is an issue, like a bad or foul odor, you should get it fixed well before summer is in full swing.


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The smells from your AC can vary and have different causes. Here is a breakdown of the smells that might linger when you turn on your AC.

1. Sour scents

If the AC releases a scent that takes you back to your high school locker room or reminds you it is time to wash your gym bag, then your AC is working with a filthy cabin filer. Stale air from your AC means the filter is saturated with dust and bacteria. To get rid of the stale air, change your cabin filter. See a step-by-step guide here.

2. Fragrant mildew

There is no mistaking the fragrant scent of mildew. When you smell it after turning on your AC, turn your attention to the under-hood air intake vent, advises Family Handyman writer Robert Lacivita. It’s most likely trapping dust, debris, and dirt.

“All kinds of nasty gunk (germs, mold, mildew) can fester and grow in that wet, trapped debris,” he adds.

3. Toxic smell

If you notice a hint of chemicals in the air, the refrigerant may be leaking from your AC evaporator, warns Lacivita.

“If you can hear the blower fan running but there is barely any air coming from the vents, oil from the leaky refrigerant has trapped dust and dirt on the evaporator fins, restricting airflow from the vents,” he explains.

4. Sugary-sweet

Just because the smell isn’t offensive doesn’t mean it’s not dangerous. Be wary of a maple syrup smell, which Lacivita says is a sign the heater core is leaking.


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If you’re experiencing any of these smells or other problems with your AC, it’s time to seek assistance from an automotive professional so your AC is ready and working properly when the temperature goes up!