Why Does My Car’s A/C Smell?

In places with hot summers like Tucson,  A/C is a necessity for a cool and comfortable drive. For many, turning on the A/C is a routine part of their daily commute and would be unbearable without it. While problems in your A/C system can disrupt the flow of cold air, others may cause you to be greeted with a musty or mildewy odor when turning the A/C dial on. Though it might still be providing you with cold air, a strong smell in your interior can make driving off-putting for both you and your passengers.

In this article, we’ll look at the potential causes of an unpleasant smell coming from your A/C vents and how you can prevent them from occurring in the future. 

Woman in car interior with hands over nose reacting to smell from the vehicle's vents

Causes of A/C Odor

Clogged Cabin Air Filter

Potentially the most common factor behind a musty smell in your vehicle is a dirty cabin air filter (sometimes referred to as the A/C filter). The cabin air filter, as the name suggests, is responsible for catching particles and contaminants in the air being circulated throughout the interior. The filter gradually builds up layers of these contaminants, and in some cases, can prevent the proper flow of clean air through your system. 

Without being able to circulate fresh clean air, the interior of your vehicle may fill with a musty or even moldy odor. This smell may only worsen when using your air conditioning or heater, as the air coming from the vents will carry this odor with it. 

The best way to deal with this issue is simple: replace the cabin air filter. Both the part itself and the labor of installing it are generally inexpensive, and can even be DIYed fairly easily as most vehicles’ cabin air filters are located in, behind, or beneath the glovebox. 

Mold Build-Up in Ducts

Though our A/C systems do their best to rid the air of any moisture, it’s not uncommon for this odor to be caused by mold growth.

Over long periods without use, any residual moisture and contaminants can provide mold and bacteria an opportunity to grow within your A/C’s tight ducts and channels. 

In many cases, this issue can be mitigated with an A/C duct cleaning spray, found at any auto parts store.

A/C dial and vents on head unit of vehicle interior

Contaminants in Evaporator

In many cases, a moldy odor stems from the evaporator. The evaporator acts as a mini radiator located towards the front of your vehicle, allowing cool air to rush over it and return the refrigerant to a gaseous state. As the evaporator uses air from its surroundings, the dust and particles present can clog the exit route. These contaminants combined with moisture around the evaporator are the perfect breeding ground for bacteria and mold. 

Normally, excess moisture within the evaporator will exit through the evaporator drain hole. This is why you’ll see water dripping under the center of the vehicle when the A/C is running. However, this hose can become clogged with dirt, debris, leaves, and other contaminants that block the passageway and allow condensation to build up within the evaporator case.

You may be able to clear the drain hose with a bent wire clothes hanger or pipe cleaner, however, debris and mold accumulation within the evaporator case will need to be cleaned with an A/C disinfectant spray or by a professional.

How to Protect Your A/C

Luckily, there are a few steps you can take to prevent issues like this from occurring in your A/C system in the future. 

  • Keep an eye on your cabin air filter 
  • Run your A/C for a few minutes each week during the winter
  • With the engine off, run the A/C fan by itself to clean out moisture occasionally
  • Avoid using recirculation mode

A/C Services at Micro Import Service

No matter the issue you’re facing with your air conditioning, the expert technicians at Micro Import Service can inspect, diagnose, and service your A/C system so you can drive cool and comfortable this summer! Give us a call or schedule online today to secure an appointment with our specially trained import vehicle technicians.