The air that comes out the air conditioning vents has mildew odor.
Possible Cause of Mildew Odor from AC Vents
Drain Pan of the AC is not DrainingOne of the key components of air conditioning in a car is the evaporator. When the ac is running the evaporator is getting very cold, then the blower will blows air through the fins of the evaporator, when the air passes the evaporators many fins the air will become cold once it comes out the ac vents.
Now, during a hot and humid season there is a condensation that is forming on the evaporator because the evaporator is cold. The formed condensation or moisture will then be dripping into the drain pan of the evaporator. Then it will be funneled down a hose into the street.
Since the problem is the mildew odor that comes out the ac vents it means that the drain pan is not draining and for the drain pan to not drain then there is a clogged somewhere on the drain pan. When the drain pan is not draining the moisture onto the street, the moisture will get trapped in the drain pan. The trapped moisture will then become a breeding ground of the algae like organism which tends to give off mildew odor. The mildew odor will then be caries by the air all the way up the evaporator going out the ac vents which will then be smelled by the driver or the passenger.
Free Car Diagnostic Recommendation
Crawl underneath the car and locate the hose going into the evaporator drain pan. You may consider looking at manual if you are not sure what the drain pan hose look like and where it is located. After locating the hose of the evaporator drain pan check if the hose if there is any clogged somewhere. Have it clean so that the moisture will drain onto the street. After the clogged is remove, wait for another couple of days before the algae like organism will dry up then the mildew odor that comes out the car ac vents will be remove completely.