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It goes from the brake booster to the octopus behind the control panel, but it is routed across the top of the airbox in clips. So it's not easy to remove the original. A replacement one could be rigged while leaving the original remnant where it is. I'll go out and check mine, take a picture if necessary.

Do this next: at the octopus, plug the black hose at the dashboard end with a golf tee or something secure, and try the vacuum pump again. If it leaks, that run of hose is bad. If it holds, the leak is elsewhere. If it's in the control unit, I can send you my spare one for cost of postage.
 

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Discussion Starter #42
Do this next: at the octopus, plug the black hose at the dashboard end with a golf tee or something secure, and try the vacuum pump again. If it leaks, that run of hose is bad. If it holds, the leak is elsewhere. If it's in the control unit, I can send you my spare one for cost of postage.
Glad you suggested the retest.
This morning, I did what you said, plugged the black hose at the octopus with the butt end of a modeling paintbrush, and tested under the hood after the check valve, and oddly enough, it holds vacuum that way. Then swapped everything around, plugged the line after the check valve, and applied vacuum at the octopus, and now it holds.
One thing I did notice last night (before the retest), is that the boot on the bottom of the check valve (heater side) was loose fitting, possibly from constant removal and re-connect, so I replaced it with a spare I had that fit better. And now, testing by applying vacuum at the octopus black hose through the firewall to the check valve, it holds vacuum.
Sorry for misleading diagnosis. I had hoped that was the cure, but...

....the problem still remains. Here's what I get, idling in the garage:

AC or'face' vents, button 1: blended air from all three points; AC vents, floor, and defrost, varies as to which is strongest, almost always weakest from face vents.

AC/Floor blend, button 2: blended air from all three again; somewhat less from the defroster and slightly stronger from floor.

Floor only, button 3: again same as above, also varies.

Defroster, button 4: air from defroster, the only button to really work. Maybe slight hint of air through face vents, not always.

I should probably re-check all the lines again, especially after the missed loose check valve boot.
 

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OK, this is good, you have good vacuum up to the control unit. Now, with the octopus unplugged, apply the vacuum pump to each of the 5 colored lines (red, brown, yellow, light green and green), and see if you can hold vacuum. As you do so, at least on the green and yellow lines, you should hear movement of the doors inside the airbox; probably so on all of them. Even if it bleeds down very slowly, it should not go to zero within, say, a minute or two. In fact, it should maybe drop only a few inches and hold indefinitely. If one of these lines doesn't hold, I'll bet the hose is unplugged at the other end, the vacuum diaphragm. I think that with some contortions, you can check them all without much disassembly. First and foremost, check the dual plug for the red and brown, which is on the left side of the airbox. You might have to remove the driver's side lower panel of the dash, but that should only be a few screws. That was a loose fit for me, and caused basically the same symptoms you're seeing.
 

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Discussion Starter #44
Ok, I rechecked all the lines and I can get all to hold vacuum, 20 to 25 inches. Can definitely hear a door opening on the yellow line, and can hear some fainter noise on some of the others. When testing the red line, it was always a little difficult to get it above 10 inches, and kept wanting to drop before it got to 10; but once it got over 10, it would hold fine. Could this be something?
 

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Discussion Starter #45
I also got up under both footwells, was able to make sure the yellow line (to the right of the gas pedal), and the dual red brown lines above the steering column were secure to their actuators. I could only see one line under the passenger side, close to the passenger door, (it might have been green); it looked fine.
 

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The right side actuator has a line each on top and bottom of it, one is green, one is light green.

I think if you apply vacuum to the disconnected octopus at each line and listen for the doors moving, that will tell if each line is good. And if they are all good, then the control unit may be what's leaking. Or one of the actuators has a bad vacuum diaphragm.
 

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Here is a diagram with color coding of the lines going to the actuators. This might give you an idea for troubleshooting purposes.

 
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Discussion Starter #48 (Edited)
Thanks for the diagrams, John. A little 'greek' at first, but once I studied them a bit, I can see what they're laying out.

After contemplating shoehorning myself under the footwells again, and maybe removing the seats to ease the blood rush to my head, to look for things I could fix... without having to remove of the dash.... I went by a local junkyard that had 1 fairly gutted '94 Lebaron convertible and a few other Mopars of that era. I picked up an AC/Heat control module from the '94 Lebaron for 12 bucks. Got home, pulled the old one, put the new 'used' one in....and.....
....the problem is solved!! No, really!
It was the AC/Heat control module after all.

Makes me kick myself for the missed diagnosis that had you guys, especially you, Bob, trying to help me with a main vac line problem that wasn't a problem. Sorry for that, really. Thanks again for everything.

Got in an drove around for about 30 minutes tonight, switching through all the settings just to be sure, but it now works fine.
It works fine.:)

I'm actually glad this happened like this. I learned a lot about this car during this process, and how some thing work on it; and I will be better for it the next time something pops up.
And I might be able to return the favor from what I've learned to someone else who has a similar issue.

I'm sure I'll need help with something else down them road; it is good to know there is someplace to go for help with these somewhat obscure cars.

Thanks again and again for all who input on this.

Thank you Bob. You da Man.
 

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Excellent! And now I'm glad I have a spare climate control module. Almost impossible to find in the northeast, because all of these older cars have been crushed long ago.
 

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Congrats - glad to see success!
 
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