Skip the auto shop - Our mechanics make house calls
  1. Home
  2. Articles
  3. Why Does the Air Coming Through My A/C Vents Smell Bad?

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

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...
Insurance Requirements for Car Registration in Kentucky
The Kentucky Transportation Cabinet requires that all drivers in Kentucky carry liability automotive insurance, or “financial responsibility” in order to operate a vehicle legally and maintain vehicle...
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: Rotten egg smell, all lights on dash board are on BUT the check engine light is off.

Simultaneous illumination of "all" warning lights on the dash while driving, when there is no underlying fault, indicates an electrical failure. That failure would have to be diagnosed in a warning light diagnostic. With regard to the check engine light,...

Q: Gas smell while driving.

Smelling a gas odor coming from your vehicle is never good experience and it usually means there is a leak somewhere. From the description provided, it is quite possible that the EVAP Purge Canister has developed a leak and needs...

Q: AC makes noise after putting on expansion valve

Hello. It sounds like your new compressor may be failing. Flushing the system is not enough when the compressor fails. When there is debris in the system, it gets stuck in the expansion valves, the condenser, and the accumulator. If...