[tjs72lemans]

I got my AC system evacuated and charged with no issues, I was looking at one last piece before putting passenger kick panel on. I noticed the flap door actuated by the diaphram doesn't budge in any control panel position. Is this flap door for fresh air or heat to come through on the heat mode? How do I check for correct function?

[OG68]

The vent door opens when the controls are set to INSIDE A/C. This allows recirculated air from the interior to reenter the evaporator, cooling the interior faster.
It also opens up in the OFF position

[Formulabruce]

2 things happen when Ac it turned on. The fresh air duct in the pass side upper cowl Opens. In the lower cowl at the kick panel, vacuum puts that flap in a position to bring fresh air to the evaporator.
In max AC mode, recirculation occurs and top cowl closes and kick panel only allows inside air.
One good way to test these is with a simple hand held mighty vac.

[tjs72lemans]

So, either my vac line to the diaphram is not getting vacuum or the diaphram is bad? The flap wouldn't open in the off or any position on controls. Maybe I should see if it will manually pull open. Maybe it's stuck after 20 years of non use.

[Formulabruce]

hooking a vac line to it and sucking on it can probably tell you something

[tjs72lemans]

I looked at this closer. I see the door is actually open as I can see the blower motor squirrel cage. So, that sounds like the mode it should be in while it is in the off position. Then, when AC and other selections are made this door shuts. I have two vacuum lines running to the diaphram. One in center and one off to the edge. Do I check one or both of these for a vacuum? I tried to see if I could manually pull the door, it's hard to get a grip on it. It does move a bit, so it's probably not stuck.

[OG68]

Do you have a 72 Service Manual? Operation and diagrams can be found in the Custom Air Conditioning chapter.

[tjs72lemans]

I do have the manual. I'll take a look.

[tjs72lemans]

Ok. I looked at the service manual and understand operation. I went through the test procedure for all the control selections and all work as should in my AC system. But, the vacuum diaphragm in the passenger kick panel does not close. It has vacuum in the line on the outside ridge of diaphragm. The center vacuum line I didn't pull off to check, as I am not sure what that one does. Does anyone know how these are suppose to function? I'd like to be able to test the vacuum diaphragm to see if it's bad before spending $80 for one.
What is the drawback if this flap door stays open and never closes? It seems all the controls function as they should. If the kick panel was on, I would never had known to check it. I'm guessing some of you out there may have the same issue and not know it.

[tjs72lemans]

I took the diaphragm out and the plastic outside was cracked around perimeter about half way around. I JB welded and clamped together yesterday and today it works as it should. Yee Haw! Saved $80! Kick panel is on and car is officially finished. For now. Thanks for everyone's input.