Hello, i remember this issue was discussed on the show but dont remember the answer ;-(. The question that whenever she turns on the airconditioner it smells as if someone has urinated in the vents. My car (2007 Audi A4) has the same problem. The urine smell lasts for a few seconds and the goes away but comes back everytime i turn it on.
do you live in suburbs, or city? are you seeing small bits of shells, hair, and other indication of mice nesting in the air ducts? you should check to see if your AC cabin filter has been changed, and if not, do that. look under the hood. check around the engine compartment for examples of mice, chipmunk nests.
Then there’s always the possibility that someone/something urinated into the vent area in front of the windshield. In that case, you might get one of the pet oder neutralizers and pour it in there, let it sit overnight, then rinse it out with a hose.
Check for leaves and crud in the area under the vents in front of the windscreen That area also has a drain that can get clogged. Some string trimmer line or a little compressed air can clear the drain. Don’t get too aggressive as you can damage the drain. The next likely area is the drain for the A/C. If it is clogged, same thing, get the drain cleared.
AC odor is a universal car problem,just not Audi.If you can look up GM TechnicalService Bulletins there are a great set of instructions on how to deal with this problem (pick any car Any year around 2000). GM has some great smelling anti- bacterial stuff too deal with this problem.