restored my heater box and installed. A gap exists between it and plastic defrost plenum that goes up to windshield. Is that gap normally open or was some sort of gasket used. Nothing was there when I took it apart but most of the old foam in heater box had disintegrated and disappeared already. Upper right of picture before removal is spot in question. Thanks.
I have found the same issue, here is the deal mother mopar didnt put recirculate air in these so with that gap it acts as a venturi pulling a small amount of cab air up and thru the system.