I get this funny smell when I turn on the heat or defrost but only after I have it on for about 15 minutes or so.
smell on 1992 Oldsmobile 98
This may be from a leaking heater core. Sometimes the smell is referred to as a "sweet" smell. Here is some more info on the heater core: http://repairpal.com/heater-core-replacement
mold and mildew also can build up in vents,producing an odd odor and allergy problems for some people, there is a spray product designed to eliminate this problem by spraying it into the outside air vent intake as you run the air for the heater or AC, I don't recommend that anyone set inside the car when doing this procedure, it can be unpleasant inside the car for a few minutes, you can get this product at several parts outlets, made by BG products, it is called Frigi-fresh, there may be other brands also