Why Does My Car AC Smell Like Mildew: Easy 7-Step Repair DIY

The pungent and unhealthy odor you sniff every time you start your car engine probably leaves you asking, “why does my car AC smell like mildew”. Well, the short answer is because of moisture and dust build up inside your AC vents.

Nothing’s more enjoyable than feeling a refreshing drive with the cool air from your turned-on AC. However, what if the smell coming from it is far from clean and fresh it is supposed to pump out?

why does my car ac smell like mildew

A mildew infection in your automobile’s air conditioning (AC) system may smell like a dirty sock, rotten food, musty, or an old dirt gym bag. Besides the unpleasant smell, inhaling it can also cause breathing problems or skin rashes, especially to people who have mold allergies.

Suppose you drive with family members who have underlying breathing problems. In that case, you’ll need to eliminate the mildew smell as soon as possible.

Fortunately, removing mildew smell is a pretty laid back task.

This article will guide you on diagnosing the possible causes of mildew smell or other nasty odors oozing in your auto’s AC. We’ll also provide helpful tips in removing and preventing it.


What Causes The Car AC Mildew Odor?

Moisture is inherent in any AC system. As the AC processes the air inside your car to produce a cooling sensation, the evaporator also collects dust particles from the auto, creating a stable food source for molds or mildew.

The humid temperature outside may also contribute to mildew growth, as it mixes with the condensation a working AC creates. This causes the molds or mildew to multiply inside the AC evaporator.

Cigarette smoke, food or drink spillage, and your pet’s stay may also add to the mildew odor. The particles from these scents may accrue and eventually clog the car’s filter as the AC recirculates the air.

The water intended to exit through the evaporator may pool in the component, making the AC unit’s interior moist all the time and, thus, luring mold-causing bacteria. If no water drips down from the evaporator while the AC is running, the AC drain is probably clogged.

A congested AC drain can also cause water leakage inside your cabin. It will soak your car carpet, which provides another perfect breeding ground for molds and mildew.

In case you struggle with this problem, follow this guide on how to get mildew smell from car carpet to help you make a quick fix.


Steps To Get Rid of Mildew Smell In Car AC

Once you know the causes of the mildew smell, it’s now time to eliminate them and get your AC to blow out fresh and cool air again. To fix the smelly air-conditioner, let these steps be your guide:


Step #1. Choose cleaning solution

You can buy odor-fighting sprays over-the-counter, or you can choose to make one on your own. If going for an all-natural spray, a mixture of white vinegar and water would be best.

Vinegar has properties that can fight off mildews. Just pour the mixture into a spray bottle; you may also add juice from half-lemon to add a refreshing scent to the solution.


Step #2. Flush mildew disinfectant spray

Before flushing the AC vents, ensure to completely switch off the car, AC, and fan. Ensure to keep the car doors and windows as you do the cleaning process.

Then, start flushing the disinfectant to every AC vent, especially in outlets that blow the most air. Do not leave out any vents inside the car.


Step #3. Switch on car and AC

After spraying the vents, re-power on the AC and set it to the maximum level. It will allow the cleaning solution to circulate all around the AC system.


Step #4. Press the recirculation button and spray into the vent

You can locate this button by going through your car’s manual. Press it (if there’s any) before gushing liberally down the cleaning solution into the vent.


Step #5. Turn car AC into fan mode

Switch the AC settings into fan mode; set it to the max level. It will enable the air to blow and lift moisture inside the car.


Step #6. Replace cabin air filters

For a graver mildew smell, you’ll want to remove, clean, or replace the air filters as necessary. Spray all the opening lines inside the system with the cleaning spray.


Step #7. Dry the car AC 

Start the car engine while the AC is turned off, but with fans switched to full mode. Do it for five minutes or until the AC vents are completely dry.

If the smell persists after eliminating it, maybe it’s time to bring your car to your dealer.


How To Prevent Mildew Smell In Car AC

To help keep you’re mildews at bay and eventually produce musty odors, follow these maintenance tips:

  1. Practice turning off the AC 5 minutes before switching off the car.
  2. Keep the fan mode on high when the car’s off.
  3. Spray the vents with mildew disinfectant at least every 3 months.

The mildew smell doesn’t exempt any part of your car. One susceptible area is your leather car seat.

Nonetheless, you can have it easy with these steps on how to remove mildew from leather car seats.



Whenever you ask, “why does my car AC smell like mildew,” the moisture pooled in the AC evaporator will always be the culprit. So, one best way to eliminate the smell is to deprive the molds and mildew of a breeding place they wanted — keep vents dry.

However, if other unfamiliar odors exist for longer days, you’ll need to bring your car to a mechanic.

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