I read an old thread regarding the use of air sanitizer to get rid of and manage the musty smell the A/C produces. Which product has been working the best to resolve the odor: lysol, febreze, or ozium?
If you live in a humid area-I do-then you will have this problem. I use Lysol because I trust the name brand. The key is getting the product into the vents under the cowl.
Also, roll the windows down, turn the car and a/c on and lower the temp button to 60. Do not put it on recirculate or Auto. Then push the a/c button-shuts off compressor-and turn the fan to high. Turn the key off only enough to shut the engine off, but leave the electronics on. Keep the blower on high and leave it be for as long as you want. You should see some fog on your windshield if it's the right humidity outside. This will dry it out a bit. I would do the Lysol after you have done this.
Or as you are about to turn into the driveway at home turn off the AC and be sure the fan/vent combo runs for 10-15 sec before leaving the car. No smell ever. You will be leaving the vent open so the heat will dry out the vents. Been working for me for years living in hot humid Atlanta.
In my experience the problem is the drain from the evaporator is clogged with either debris or an algae build up allowing water to be captured in the heater creating algae and or mildew do accumulate. This can also be a health hazard. have you ever heard of "Legionaires Disease"?