Mildew Smell in my Car's Air Con.

How it the world can I clean and prevent this? Besides covering it up with air freshner and not using the air conditioner.

Treatment? Tom & Ray covered this in Car Talk. Spray a 10-second burst of Lysol aerosol into the A/C intake next to your windshield, keeping the A/C running. This should kill most of the mildew spores and suppress most of the rest. If smell persists, repeat. Make sure you air out your car for a couple days, as this isn’t the kind of stuff you want to be deep breathing while driving.

Prevention? Probably can’t. Some cars are more prone to this than others.

Make sure the evaporator coil drain is clear and clean. This could take a few hours - probably have to remove the cover to expose the coil

Also important to do in the home units - lots easier too.