Your vehicle’s air conditioning system does not actually create cold air; it takes heat and moisture out of the air that is outside of your car, which in turn, makes it feel much cooler than the air around you.
The coils in the AC unit work to condense the heat and moisture in the air, taking out the humidity before pushing the cooled air into your car.
As these coils are colder than the air around them, hot air flowing into the unit can create moisture pockets that surround the condensing unit in your AC system; which create small pools of water that are drained outside of the car via the drain line.
However, if moisture becomes stuck or for whatever reason cannot find its way out of the AC unit, by drainage or evaporation, the water will pool inside the unit and around the coils creating moisture inside of the AC unit.
Mold is the Cause
If your drain line is damaged or you frequently use your AC system, the unit is likely to stay damp all the time, which creates a breeding ground for mold and bacteria.
The air that passes through the evaporator and the units’ mold build-up will carry the foul smell inside of your car through your dash vents.
Mold is the most common culprit for causing raunchy smells to come out of your cars’ AC.
As a vehicle gets older, bacteria, mold, and other unwanted micro-organisms can start to grow. If the AC unit is not often used, or used much too often, this can also increase the growth of these microbes inside your car’s AC system and ventilation system as a whole. Odor-causing mold loves to reside in your cars’ AC unit because it is always moist and dark – ingredients for a happy home for mold.
If you checked on your drain tube and tried to clear out mold yourself with no prevail – all is not lost. You don’t have to replace your car, but you MIGHT have to replace the AC unit in it. Bring your car into a trusted dealership or repair shop to have your AC unit assessed as soon as possible.