I replaced the air filter 2/3 months ago.If your car AC smells like mildew or mold, it almost certainly has actual mildew or mold! Bacteria grows in the system where moisture typically collects — especially on the A/C's evaporator.
If your mold or mildew problem seems mild, there are over-the-counter remedies available. If you're looking for something with an easy application, try a vent and duct cleaner you can spray into your vents to help neutralize the odor. For a long-term solution, the system needs to be taken apart & parts cleaned. Also, the interior air filter needs to be replaced.
I cannot for my life find where the condenser hose is to spray kool-it into it. I looked online at so many images and could not find it.