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Why Your Car AC Smells Like Feet – Fixes and Prevention

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It’s safe to say that air conditioning is a great invention. Unfortunately, bacteria and fungi think so too. Overusing and neglecting to clean the car’s AC system regularly could lead to bacterial growth, which causes your car’s AC to smell like feet, musty, fishy, sweaty, and even lead to health issues.

What Causes Your Car’s AC to Smell Like Feet?

The cause of your car’s AC smelling bad is moisture, which creates the perfect breeding ground for fungi and bacteria.

Your car cools the air inside the cabin by blowing air through the ice-cold evaporator (a small radiator behind the glove box). The car’s evaporator removes heat from inside the car’s cabin by absorbing the heat and the moisture that’s in the inside air.

Because of this, pools of water collect on the surface of the evaporator. To drain this moisture, engineers fitted a drain tube, which is routed under the car – this is the reason why cars leave puddles of water during the summertime. 

If the moisture gets trapped inside and does not drain out from the drain tube – perfect conditions for mold and bacteria are created (darkness and humidity).

It’s Harmful To Your Health

Airflow from the blower motor carries mold and bacterial particles into the vehicle’s cabin. Small amounts of such particles are completely normal and shouldn’t cause health problems, however, studies show that breathing in large concentrations of fungal and bacterial particles that are growing on AC systems could result in a variety of adverse health issues, such as:

  • Nose and eye irritation
  • Asthmatic reactions
  • Allergic inflammations

Air conditioning systems in cars should be regularly cleaned and disinfected in order to eliminate bacterial and fungal contaminants that could cause health issues.

How To Get Rid Of Bad Odor in Your Car’s AC

Small amounts of bacterial growth in the car’s AC system is normal as the evaporator is located in a dark and humid area. However, if your car’s AC system contains large colonies of bacteria and gives off a strong musty, sweaty or fishy odor you will have to clean and disinfect the evaporator.

Cleaning and disinfecting the evaporator is a DIY job. Evaporators are cleaned with special evaporator cleaners.

They take care of the cause of the bacterial growth by injecting the cleaning foam through the vehicle’s drain tube, which unblocks it, meaning that the humidity will no longer pool up near the evaporator and will drain out of the vehicle. When the cleaner makes its way onto the evaporator it foams up to reach every area and kills the microorganisms while also dissolving any grime.   

Evaporator cleaners come with a detailed user manual or an instructional video, which outlines the whole process in detail for the specific product.

Most of the time, the cleaning process doesn’t require any tools and could be completed in under 30 minutes. In case you don’t want to do the job yourself, your local mechanic will be happy to do the job for you.

Clean vs Dirty Cabin Air Filter
A dirty cabin air filter is food for bacteria!
Photo by Ryan Gsell | (CC BY 2.0)

Make sure to change the cabin air filter after cleaning the evaporator. The cabin air filter is designed to catch all the nasty particles and prevent them from entering the inside of the vehicle. Over time, the filter collects pollen, road grime, bacteria and if not changed regularly, could increase the likelihood of bad odor coming back.

How To Prevent Bad Odor and Bacterial Growth

After you’ve cleaned the car’s AC system from nasty and smelly microorganisms, be sure to minimize the likelihood of the bacteria coming back.

  • Check if the drain tube is working. Doing this is very simple. A working drain tube lets water drip from under the vehicle onto the ground. If there is water dripping from under the car when the AC is on, your car’s drain tube is working as it should.
  • Let your evaporator dry out. Before the end of your trip, turn off the AC and let your blower motor dry out the moisture for at least 10 minutes. Some cars have this feature and do it automatically approximately 30 minutes after you shut off your engine.
  • Replace your cabin air filters. This is often overlooked but replacing your cabin air filter makes a big difference. The cabin air filter is designed to capture and prevent dust, pollen, and other contaminants from entering the cabin. Since the filter collects all kinds of contaminants it could act as a source of food for mold. For best results, replace your cabin air filter with an Active-Carbon air filter as they are considerably more effective at purifying the air and preventing bad odor.

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