Hi Folks,
I'm replacing my cowl plenum air inlet door and actuator (this is the plastic flap with actuator mounted to it on the upper right hand side of A/C cars that controls the amount of outside air entering). I'm having trouble getting the door to seal properly when vacuum is applied. In the open position (no vacuum applied) the plastic door drags substantially inside the plenum and puts up too much resistance to close. If I trim the plastic door so that it clears the channel it is too small to seal the opening as there are gaps around the edges where I had to trim. I think the problem in part is that the reproduction part isn't that great. When you look at an original door it isn't perfectly symmetrical, it's shaped differently on the upper vertical edge than the lower whereas the reproduction is symmetrical. So, I think in part my problem is that I need to more carefully trim the reproduction part to mimic the original but still not sure this will result in a perfect seal. I have two specific questions for someone familiar with this component:

1. Am I overthinking the need for a perfect seal when vacuum is applied or is this a case where near enough is good enough?
2. Did the car originally have some sort of foam or rubber seal mounted around the opening of the plenum to help the door seal or is it supposed to seal against the bare fiberglass?

Hopefully this question makes sense
Thanks in advance.

This is the assembly I'm referring to. The door (item 7) hinges on its RH edge inside the plenum and seals against an opening when vacuum is applied the actuator. I needed to trim a 1/4" from the top and left hand edge in order for the door to move freely, however once trimmed it is no longer large enough to seal the opening without a gap on the trimmed edges.

 

I am not sure about whether it is plastic or rubber.
But I do know how that door works.
It just shuts off the outside air, and only when the A/C is put into recirc mode.
At all other times it is open to admit fresh air.
So do I think it is important for it to seal perfectly? Nah.

 

I am absolutely certain that on my car from new. It does not seal perfectly.
Back when I updated to a C4 blower motor and was working in that area. I installed some of that foam with the peel and stick on one side.(to the door frame, not the door itself). You know the stuff from the hardware store for sealing drafts. It's really a soft foam, about 3/8th's wide by about 1/4 inch thick. Just to help the door seal better. It's still not perfect. But the door is only closed on Max air and it seems to work just fine.

 

That's helpful to know, thanks! Yes, I know the foam extremely well and its exactly what I was thinking I might add to mine. The Corvette Parts and Illustration Catalog has a foot note to dealers about "not disturbing the foam seal" in reference to assemblies in that area which is what made me think there might be a seal installed at he factory, however it did not reference an actual part for the seal which it usually does. Seems to me there is no harm adding self adhesive foam to help the seal along a bit. Over the winter I restored the A/C in the car to factory original that had been deleted by the PO so I want to give it the best chance of running cool. (It's hot where I live).

 

I'm thinking you're right. Thanks for the opinion.

 

just went through this on my car. had to trim little bit at a time until no drag. there’s definitely a gap now but again it’s only shuts when on a/c max for recirculating air in the cabin.