I have a 2000 suburban 2500 and just recently there has been a strange smell coming from the AC vents when the AC is running and the suburban is at idle. There is a faint smell when running at normal speeds but at idle there is a burning smell and at times almost smells like wet dog crap. Like I said a really odd odor. I don't drive the suburban like I used to, just mostly for towing the boat so it does sit for a week or 2 at a time. Just curious what some opinions may be.