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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Peter

25 years of experience
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Peter
25 years of experience
Ford Explorer V6-4.0L - Smell in the car - Canyon Country, California
Wonderful experience!! He explained all the issues that my car was having so that I could understand!!! I will be calling on Peter in the future to fix all of my automotive concerns!!
Volvo 850 - Smell in the car - Simi Valley, California
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27 years of experience
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Ford F-150 V6-3.5L Turbo - Smell in the car - Texas City, Texas
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Adam

17 years of experience
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Adam
17 years of experience
Mercedes-Benz 380SL V8-3.8L - 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
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Jeep Grand Cherokee V8-6.1L - 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!

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