Skip the auto shop - Our mechanics make house calls

Why Does the Air Coming Through My AC Vents Smell Bad?

ac smell

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’re noticing strange smells coming from the AC 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 AC and shutting off the engine.

Mildew can thrive in many areas of your car’s AC 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.

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 AC 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. The cabin filter(s) can be found behind the glovebox, but it takes a considerable amount of teardown to remove and replace them.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Skip the repair shop, our top-rated mechanics come to you.

At your home or office

Choose from 600+ repair, maintenance & diagnostic services. Our top-rated mechanics bring all parts & tools to your location.

Fair & transparent pricing

See labor & parts costs upfront, so you can book with confidence.

12-month, 12,000-mile warranty

Our services are backed by a 12-month, 12,000-mile warranty for your peace of mind.

Get A Quote

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!

Need Help With Your Car?

Our certified mobile mechanics make house calls in over 2,000 U.S. cities. Fast, free online quotes for your car repair.


Post a question and get free advice from our certified mechanics.


More related articles

How to Find the Keyless Code on a Ford Explorer or Mercury Mountaineer
Many Ford Explorers and Mercury Mountaineers were manufactured with an option known as the Ford keyless entry keypad. Some models refer to it as SecuriCode as well. It...
P0222 OBD-II Trouble Code: Throttle/Pedal Position Switch/Sensor B Circuit Low Input
P0222 code definition Throttle/Pedal Position Switch/Sensor B Circuit Low Input What the P0222 code means The manufacturer specifies a range of acceptable voltage to be produced from the throttle position...
Veteran and Military Driver Laws and Benefits in Idaho
The state of Idaho offers a number of benefits and perks for those Americans who have either served in an Armed Forces branch in the...

Related questions

Q: How do I adjust the cabin temperature?

The cabin temperature is controlled by the Temp switch in the climate control settings. Press the upwards-facing arrow on the switch to increase the temperature, or press the downward-facing arrow to decrease the temperature.

Q: Why Do Some Exhausts Smell Bad?

The most common reasons for an exhaust system to smell bad is the result of the thermal reaction that occurs within the catalytic converter. The temperatures inside catalytic converters run around 1200F to 1600F. The front substrate inside the catalytic...

Q: Squeak/screech noise, burning smell

This may very well be related to the catalytic converter in your car. As you know, the catalytic converter is responsible for converting toxic combustion gases into less harmful gases to be dispelled into the atmosphere via your car's exhaust...