Hey guys.

I have a very interesting issue with my heat. When I have the heat setting set to "HI", everything is just dandy. Once I lower the temperature from HI to 85, etc., an odd odor start to emanate from the vents. If I put the heat back to HI, the smells goes away immediately. This issue has plagued my car for a while now. AC is fine as far as I can recall. Air cabin filter has recently been replaced with no change. Any ideas?

Thanks