Why Does the Air Coming Through My A/C Vents Smell Bad?

When you turn on your car’s air conditioner, you should receive a flow of cold air that cools the cabin. It shouldn’t have any discernible smell. If you notice strange smells coming from the air vents, there’s a problem. The actual nature of that problem will depend on what you’re smelling.

Causes of bad odors

If you’re smelling a musty/moldy smell (think dirty socks), then what you’re smelling is mildew growing in the system. This is actually a very common automotive problem, and it’s generally caused by running your air conditioning system only on recirculate, and not blowing the fan for a minute or two after turning off the air conditioning and shutting off the engine.

Mildew can thrive in many areas of your car’s air conditioning system, but you’ll find it’s particularly fond of the evaporator core and the condenser. These areas are moist and enclosed – the perfect habitat for bacteria. While it doesn’t really present much of a health risk, it certainly is unpleasant to smell.

How to prevent bad smells

There are several ways to treat this, but the best solution is not to experience it in the first place. Always switch between fresh air and recirculated air to help dry out the interior of your car’s HVAC (Heating, Ventilation, and Air Conditioning) system. Additionally, always try to run the fan without the air conditioning on for at least two minutes before turning off the engine (again, this is to help dry the system and avoid creating a habitat conducive to mildew and mold growth). The problem can also be treated by spraying a disinfectant through the fresh air intakes under the hood, as well as using a foaming system cleaner (both of these should be done by a professional).

Another potential cause here is that your cabin filter(s) needs to be changed. The cabin filter does the same job as the air filter under the hood, but it’s responsible for filtering the air that makes its way into the cabin. Over time, the filter becomes clogged with dirt, dust, and pollen. Mold and mildew can grow here as well. Some cabin filter(s) can be found behind the glovebox, but it takes a considerable amount of teardown to remove and replace them.

If you need assistance inspecting or repairing your air conditioning system, contact a certified mobile technician from YourMechanic.


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John

27 years of experience
800 reviews
John
27 years of experience
Ford F-150 - Smell in the car - Texas City, Texas
John is the best in our opinion. He is professional, knowledgeable, thorough, timely in arrival and in doing the job. We appreciate him.

Adam

17 years of experience
126 reviews
Adam
17 years of experience
Mercedes-Benz 380SL - Smell in the car - Delray Beach, Florida
I highly recommend Adam. He totally understood the vehicle and the various different elements that needed to be fixed. Even items I did not know about. Very appreciative of the service and would highly recommend!

Miguel

2021 years of experience
28 reviews
Miguel
2021 years of experience
Jeep Grand Cherokee - Smell in the car - Orlando, Florida
Miguel was able to arrive several hours earlier than expected which was a great surprise. He was very professional, knowledgeable and provided excellent advice on additional issues. Thank you Miguel!

Michael

22 years of experience
67 reviews
Michael
22 years of experience
Hyundai Equus - Smell in the car - Las Vegas, Nevada
Michael was very courtesy and checked everything to find the smell recommended dryer sheets for now and will be arming estimate for evaporator as everything else was good. Will recommend Michael to family & friends or anyone in need of car repairs. Oh Michael also came with a mask on which was also appreciated thank you

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