Does Your Truck's Air Conditioner Stink?

Tips to Help You Avoid or Eliminate Smelly A/C Odors

Truck at Sunset
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Taking Care of Your Truck's A/C System

Do you notice a strong, mildewy smell when you first turn on your truck's air conditioner? If the answer is yes, you aren't alone.

One of the A/C system's most important jobs is to remove moisture from the air. The moisture becomes caught in the A/C's evaporator (a unit in the dash that looks like a radiator) and condenses to water on the evaporator's fins. The water runs down to the bottom of the box holding the evaporator before exiting through a drain tube, where it creates that puddle you see under the truck when you park it after using the A/C.

The higher the humidity, the more moisture the A/C grabs from the outside air. Unfortunately, some of the moisture sticks around, clinging to the fins when the vehicle is turned off, and making those damp spots a perfect breeding place for mold and mildew as temps in the parked truck rise.

There's no sure way to completely prevent mold and mildew from developing in the evaporator, but it helps to turn the A/C switch to outside air before you turn the truck off. Doing that allows some of the moisture to escape, and keeps the truck's interior a little cooler than it would be if the switch is left in the recirculate position.

If the A/C already has an odor, you'll need to clean the evaporator (it's usually best let a dealer or trusted repair shop perform the cleanse).

An evaporator cleanse is normally a three-step process.

  1. A tube is inserted into the evaporator and used to fill the unit with disinfecting foam.
  2. Next, the tech shoots a cleanser into the evaporator box to clear out the foam (and the dissolved or loosened mold and mildew).
  3. Finally, an air freshener/antibacterial product is inserted to help discourage build-up of new mold and mildew.

A cleanse might be necessary every year or two, depending on the truck, the design of the air conditioning system and the way you use the A/C.