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Well, since working on the vacuum hose made the problem worse, it points to being a vacuum issue. The airflow will default to defrost if there is low vacuum. You may have to go through all the lines, but it seems likely the problem is under the hood, rather than in the dash. I think there are some hard plastic lines involved that could be cracked/brittle from age by now.
 

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Discussion Starter #22
The hose dangling from the firewall - could that be the rubber elbow that is your A/C condensate drain? It attaches with a spring clamp to the drain pipe from the heater box, which exits the firewall near the passenger side about halfway down the firewall. (looks like the rubber hose behind the brake lines in this photo): http://i1225.photobucket.com/albums/ee385/RT_Rob/HeaterCore040.jpg
http://i1225.photobucket.com/albums/ee385/RT_Rob/HeaterCore040.jpg

Thanks Bob,
and yes, that is the one, exactly the same on the 3.0. I thought that since the one pictured, and the one from the lowest air box position terminated in very close proximity to each other, that they may connect together. Someone else must have thought the same thing as well; I was at the junkyard Tuesday and the one Lebaron 'vert that was there had those two hoses connected; though it was laying on the ground under the car.

If you are in defrost mode all the time, there is a low-vacuum situation or leak from the hose that goes to the climate control, the one that you found severed.
I hope it's a leak from the hose...otherwise, from what I understand (especially from neonrt98), I'll need to remove the dash, which I'm not looking forward to.

Oh, and BTW neon, I totally forgot about that trick about checking plug wires in the dark. I had a '71 Roadrunner 440 back in the '80's, had a miss issue, and that method was helpful in fixing it.
Blast from the past. :D
 

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Usually, the semi-flexible hard vacuum hose does not crack under the dash (less heat exposure), but under the hood that line can be very brittle. I've patched a split in one area, only to cause another in a different area just by moving the hose a little. I believe I used windshield washer spray tubing to splice cracked sections of tubing.

If you do find a leak under the dash, it might be caused by a disconnected hose at one of the vacuum actuators, or at the vacuum junction block connector going to the HVAC panel. That connector block for the HVAC panel can usually be accessed by removing the glove box and the HVAC control panel unit. Try removing the glove box first and shine a flashlight to the left to see if the vacuum junction block is visible.

On rare occasions, the HVAC unit can go bad and leak. A hand held vacuum pump can be a valuable tool for troubleshooting the problem and identifying the leak. With a hand held vacuum pump, you should be able to test all the door actuators for operation and any vacuum leaks.
 

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No need to remove the glove box on the 92 Lebaron to access the vacuum "octopus". Just pull the center panel off the console and unscrew the climate controls, and pull them forward a little.
 

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Good call on the AC drain, was going to suggest that was the case but I am days late. Also note that both of my Sebrings ('05 and '06) had that hose fall off and the fitting fail, causing a very wet passenger floor! No issue with the '92 Shadow however since it isn't (and won't have) AC running.

I did note that the small hose running from the check valve/vac booster to the firewall on the Shadow is very neatly severed as well. Something else to chase once I get the basics (brakes, starting, running) up to snuff.
 

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Discussion Starter #26
Thanks everyone for all the replies. really learning alot here.

Anyways, a little progress so far....I was wrong about 'making sure the vac line was open' in an earlier post; it was still pinched at the check valve. I opened it up with a combination of a safety pin, toothpick and a small furniture nail. Put the check valve back on, fired it up, and air came out the vents like it's supposed to. Got down the road a little bit then it began to cycle to the floor then back to the vents. It would go thru the defroster only when I selected defrost; otherwise it just cycles through floor and vents. better than it was, but....
Is the vac line removeable right there at the firewall? Is there a nipple I can't see behind that foam-type jacket where it meets the firewall? I tried to pull on it with moderate force, but I didn't want to break it and be in worse shape. I have a replacement, just unsure if I can just yank it off at the firewall.
 

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Discussion Starter #27
Different (wrong again) on the next trip today. 50 mile round trip. AC and fan on full went from defrost to footwell. Sometimes both at the same time. Never full output from the 'face' vents. Rarely any output from the face vents.:(
 

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That vacuum line goes from the check valve at the brake booster, through the foam block where the heater core tubes are, is bundled with the other vacuum tubes for the airbox's vacuum actuators, and up to the dash to the 'octopus' connection of vacuum lines behind the climate control panel. It's one hose all the way.
 

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Discussion Starter #29
That vacuum line goes from the check valve at the brake booster, through the foam block where the heater core tubes are, is bundled with the other vacuum tubes for the airbox's vacuum actuators, and up to the dash to the 'octopus' connection of vacuum lines behind the climate control panel. It's one hose all the way.
So..I gather from what you're saying...I can't just yank the small vacuum line that's connected to the check valve away from the fire wall because the same line, with no breaks, continues up into the dash, with no different attaching point?

The check valve and vac line I pulled from the junkyard...it was from a '94 LeBaron 'vert...the vac line looked like it to pulled out of a hole in a black plastic box behind the foam jacket that surrounds those fittings. Since I have a '92, I'm unsure if Chrysler changed anything for those years. The line I pulled has no leaks, and I have no means right now to test the one on the car without pulling it out. Can anyone be specific as to which other vacuum lines I need to test?

Thanks again.

John
 

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If you have a hand vacuum pump, first thing to do is connect it to the line that goes to the check valve and pump it to 20 inches. If it does not hold, or bleeds down within seconds, that line is broken, or one of the other 5 vacuum lines to the airbox is disconnected or broken.

If the line holds vacuum, then you should be able to punch the climate control buttons and hear the doors move in the airbox, which direct the airflow to defrost, or vents, or heat. If you don't hear any doors flopping, then something may be stuck.

I have pictures at home of the airbox and vacuum lines, from when I replaced my heater core recently. Will post late tonight when I get a chance. But you have 5 vacuum lines behind the dash that control the directions - red, yellow, brown, light green and green tubing. Then the black line from the check valve runs to them all to supply vacuum. Pushing the climate control buttons directs the vacuum to the correct tube. If you remove the center panel from the console (just pull straight back, hard), you will see that you can remove two screws and pull the climate control unit out a little, enough to see what I call the 'octopus' connection of vacuum hoses. Make sure that that rubber connection is tightly plugged together.
 
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Discussion Starter #31
If you have a hand vacuum pump, first thing to do is connect it to the line that goes to the check valve and pump it to 20 inches. If it does not hold, or bleeds down within seconds, that line is broken, or one of the other 5 vacuum lines to the airbox is disconnected or broken.

If the line holds vacuum, then you should be able to punch the climate control buttons and hear the doors move in the airbox, which direct the airflow to defrost, or vents, or heat. If you don't hear any doors flopping, then something may be stuck.

I have pictures at home of the airbox and vacuum lines, from when I replaced my heater core recently. Will post late tonight when I get a chance. But you have 5 vacuum lines behind the dash that control the directions - red, yellow, brown, light green and green tubing. Then the black line from the check valve runs to them all to supply vacuum. Pushing the climate control buttons directs the vacuum to the correct tube. If you remove the center panel from the console (just pull straight back, hard), you will see that you can remove two screws and pull the climate control unit out a little, enough to see what I call the 'octopus' connection of vacuum hoses. Make sure that that rubber connection is tightly plugged together.
Okay, I picked up a hand held vacuum pump, that came with a few 'press in' fittings. All I really had time to do is check the check valve (held vacuum one way and let is pass the other way), so it's good. The line leading into the firewall will not hold and vacuum. I checked it closely for cuts or crimps but could not find any. I guess it's time to take the front panel off.

Looking forward to seeing the pictures you have, Bob.

Your help is (and everyone else's) is greatly appreciated.
 

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I will bet that a vacuum line inside fell off one of the actuators. I had the red-brown one fall off, that was still very loose, enough so that I'll be wary of it falling off again.

Here's a photo showing the various vacuum lines. The green and light green go to the lower right actuator. The yellow goes to the left one nearest the driver's feet. The brown and red are connected, molded together and connect to a vacuum actuator on the left side further back, the one that pulls on the rod that you see on the top left of the box. All of them, including the black one from the firewall, bundle together and come together in a clear rubber connector, which in this picture is lying on top of the actuator at the top left side of the airbox cover. That's what plugs into the back of the climate control panel.

 

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I don't know if there is a plastic vacuum line connector behind the controls like on the older cars, but they tended to crumble away to nothing.
 

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These are clear rubber, they stay pliable.
 

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These are clear rubber, they stay pliable.
They don't always stay pliable. They get old and brittle and can crumble when disturbed. At least they did on older cars. Maybe they reformulated them or maybe only certain environments affect the connector.
 

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They don't always stay pliable. They get old and brittle and can crumble when disturbed. At least they did on older cars. Maybe they reformulated them or maybe only certain environments affect the connector.
Concur... especially for those cars in the South that are parked outside. I came across vacuum tubes right at the heater control junction block that had split right where they attach. These were on 80's models, so there may have been improvements on 90's vehicles with better tubes.
 
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Discussion Starter #37
I will bet that a vacuum line inside fell off one of the actuators. I had the red-brown one fall off, that was still very loose, enough so that I'll be wary of it falling off again.

Here's a photo showing the various vacuum lines. The green and light green go to the lower right actuator. The yellow goes to the left one nearest the driver's feet. The brown and red are connected, molded together and connect to a vacuum actuator on the left side further back, the one that pulls on the rod that you see on the top left of the box. All of them, including the black one from the firewall, bundle together and come together in a clear rubber connector, which in this picture is lying on top of the actuator at the top left side of the airbox cover. That's what plugs into the back of the climate control panel.
Ok, so I got the temp control unit pulled out enough to see the clear plastic connector a few inches behind the unit. Still very pliable, with what seems to be a very light film of some type of grease or oil on it...(maybe to keep it from drying out)?
Disconnected the plug.
From here I'm guessing I hook my vacuum tester to each individual line and they should all hold vacuum except the one (or ones) that have failed?
I tried that, but the smallest fitting that came with the tester is just a bit too big to fit in the ends of the vacuum lines. That grease isn't helping either. I got it to stay in one line (I think it was a black one), and it held. I'm either gonna find a smaller fitting, or try and alter the one I have to fit in the ends of the lines.
I will certainly let you guys know what I find.
 

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Correct, if you can apply vacuum to each, and it holds, then the tubes are intact as are the vacuum diaphragms into which they plug. Be careful not to damage the octopus, it's a junkyard item only.

But since you said that the vacuum line through the firewall won't hold vacuum, there must be a leak somewhere.
 

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Discussion Starter #39
Correct, if you can apply vacuum to each, and it holds, then the tubes are intact as are the vacuum diaphragms into which they plug. Be careful not to damage the octopus, it's a junkyard item only.

But since you said that the vacuum line through the firewall won't hold vacuum, there must be a leak somewhere.
Yeah, the line thru the firewall didn't hold any vacuum at all, the gauge dropped immediately.
I have a some "life-getting-in-the-way-of-things-I-want-to-do" things I need to get out of the way tonight, then maybe with a little luck I'll be able to run a productive test tonight.

I really, really appreciate the time, effort, and info you and others have provided here.

thanks again,

John
 

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Discussion Starter #40
I used a Dremel tool to alter the tip of one of the vacuum tool fittings to fit tighter into the 'octopus' vac line cluster lines inside the car. It seems the black line is the only one that will not hold vacuum. A couple others dropped vacuum very slowly, but I attribute that to the modified tool tip probably not being exactly round. The black line drops immediately; never even begins to hold. This line goes out to under the hood to the check valve, correct? Is there any way to access this line from the footwell, or does the dash have to come out?
 
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