There is a TSB on this subject that provides part numbers to add an "after blow" kit. I just tried looking up the TSB, but the site is down. The dealer should be able to find in on OASIS with an air conditioning problem code.
The "after blow" is a control module that runs the A/C blower about 1/2 hour after shutting off the engine to dry out the plenum. I don't know of anyone that has tried it on our cars, but it works very well on other makes, such as some GM products and Volvos. For some Volvos this was the absolute answer. This system is a little pricy if you needed to pay for it yourself if the car is out of warranty.
If you don't add this kit, it does help to change the cabin filter. It also helps to deoderize the system at the same time. If you are doing it yourself, it is hard to find the best deordizer for home use, but Lysol works reasonably well. With the cabin filter removed, turn the A/C fan on at a low speed, continuesly spray Lysol into the hole where the cabin filter belongs for about a minute, then shut the fan off and allow the Lysol to soak in for at least 30 minutes (overnight is not too long) while you install the new cabin filter. You want the Lysol to soak into the walls of the case as well as the A/C evaporator core.
Best of luck with this.
