Originally Posted by sstevens7

Moisture is building up in the air filter when you run the a/c and if you just shut your car off that moisture sits in the filter accumulating bacteria causing the smell. I think this has been discussed on here before. What people say to do is about 5 minutes before you reach your destination turn the a/c off and run the heater to dry out the filter so it doesn't have the opportunity to start to smell.