Looking for ideas before I dismantel the heater vents.

When I turn on the front heater in my 96 Suburban it has a tough smell. It was a work truck used to carry weeds that stunk, so that is the odor I think I smell (not anti-freeze).

When heater is off (or on the blue setting) the smell is not there.

Is there a cabin filter that may just be saturated by the old weed smell?

 

They didnt install cabin filters till 99. What you smell may be the ventalation from the a/c producing condensation and creating the mildew inside. Try some BG Refrigerant. Its a spray can that eliminates the odor from corroded ventalation. Other than that, you will have to replace it.