[dld]

Fitting heater A/C duct work in my car . The defrost plenum does not seal to the heater box . there is a 3/4 space or gap between the to . yes i see the piece missing from a prior owner repair?? But is there something missing

See Pic

[fbody_mike]

I am about 80% certain there is supposed to be a gap like you have there. I always assumed it was to allow the M&Ms that roll down the defrost vents a way out so they are not trapped in the ducts (you need to watch the movie Tommy Boy to get the reference).

[TacoTownCharlie]

I noticed the same thing in my 78TA. I don’t think those parts were designed to fit together. The gap allows you to find small objects that fell into the ducts from the dash and also to mix cabin air with the defog/defrost air. Hopefully someone else will weigh in to confirm or deny.
TTC

[unruhjonny]

isn't there supposed to be a thin metal strap of sorts that connects the two parts - while keeping the gap?

[dld]

[QUOTE=fbody_mike;6223329]I am about 80% certain there is supposed to be a gap like you have there. I always assumed it was to allow the M&Ms that roll down the defrost vents a way out so they are not trapped in the ducts (you need to watch the movie Tommy Boy to get the reference).[/QUOTE

Yes, I did like that movie. HA HA . I'm OK with the gap but was thinking there was a foam seal . I'm making a repair bracket that will secure the two together as was. Makes sense. There is a grill on the defrost feed plenum above the door

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[dld]

OK bracket made . still room for the M&M's to trickle out under drivers feet.

Thanks To all

[Formulabruce]

The gap is factory and is engineered into the HVAC system. It actually sucks in cooler, dryer air while defrost is on to keep window from fogging up in humid environments. This allows a sort of "blend" affect without moving the control to blend.