Its for my 73 Blazer with A\C I started ripping at it and found that the plastic piece that opens the flap is broken.
Thanks Rocknutah for the part number I will be needing that part

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I started ripping into it for a very short time because its sleeting outside and dark, it's my DD so I cant afford to go without the heat(It works just doesnt switch to the defrosters on top).
I found that there was a small rodents nest inside and cleared it out the best i could see.
The hot air comes out of the peice by the floor(Middle section) and one of the center airducts through the dash but not the top piece as mentioned before or the other ducts.
When I try and open the vent flap it doesnt open I see that its ran by an orange lined vacumme line but im not getting anything out of it(Located on the passenger side where the kick panel is).
Really all I need is a diagram of where all of the vaccume lines go because I think that is one of the problems other than that plastic peice that's busted.
One of the vacume line i traced to an outside (in the engine compartment)
valve thinga majigger above the fan.
I would like for the heating\ac functions to all work properly as im tired of waiting for it to melt the ice and heat up the truck.
Thanks for all the help looking forward to hearing some opinions on what else to look out for on these heating systems as far as things that are prone to wearing out and such.
Everything is factory as far as heating in this truck but the ac compressor has been ripped out though.