Skip the auto shop - Our mechanics make house calls

Why Does the Air Coming Through My A/C 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 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.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
Icon-warranty_badge-02

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

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.

GET A QUOTE

More related articles

How Long Does a Fuel Filler Neck Last?
Getting gas from the pump to your gas tank is the only way to keep a car going. The fuel filler neck is a metal tube that is welded to the...
Symptoms of a Bad or Failing Flexible Clutch Hose
Common signs include difficulty shifting, low clutch fluid, and feeling no resistance at the clutch pedal.
P0052 OBD-II Trouble Code: HO2S Heater Control Circuit High (Bank 2 Sensor 1)
P0052 code definition HO2S Heater Control Circuit High (Bank 2 Sensor 1) What the P0052 code means This code is seen when the Engine Control Module (ECM) tries to control the...


Related questions

Q: Moldy smell from AC at startup

Hello, thank you for writing in. The best way to remove a moldy smell from your vehicle's air conditioning system is to replace the evaporator. This is a very time consuming and expensive repair, but is the only way to...

Q: Smoking and smell of antifreeze

If you engine just started to pour white smoke out the exhaust then most likely you just blew your head gasket. It could be from overheating or corrosion inside engine caused the head to leak coolant into the cylinders and...

Q: My AC bearings are making noise - what does this mean?

Hi there. I am not quite clear which bearings or other components you may be hearing. The most likely noises coming from the engine compartment would be the AC compressor clutch bearing, and the compressor itself. While the clutch bearing...