HVAC under-dash vacuum lines question

Interior and Electrical

  1. rcmaniac791

    rcmaniac791 Well-Known Member

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    What's up everyone, got a bit of a question here.

    I began working on the A/C in the 5th again today, and when I turned on the air, I only got airflow from the defrost, not the vents on the dash. I couldn't redirect the airflow to save my life.

    So I took out the panel under the driver side of the dash, and little green chunks of what used to be rubber fell out, and I noticed that the color-coded vacuum lines were all hanging, disconnected. I'll attach 2 pictures for a reference.

    I know that finding another green connector will be near impossible, and I'm pretty sure that I can simply re-attach the colored vacuum lines to their corresponding black line using some small pieces of rubber vacuum line, I just don't know what the order of the colored lines is in order to reconnect them properly. Does somebody have a picture of this assembly that is still in tact so I can reference that? Any other tips? Thanks.

    BTW, I did cap off the pink line, since I determined that was the vacuum signal, and I didn't want a vacuum leak.

    IMG_1176.JPG IMG_1175.JPG
     
  2. Dr Lebaron

    Dr Lebaron Well-Known Member

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    Another board


    I use vac tubing to bypass the rotted connector.
    as long as the colors go to the right ports it will work.
    The one with the x has nothing going to it.
    and a red one is on the other side of the connection going to the empty spot.


    Left to right top 3
    Brown, Yellow, Lt Green


    Left to right bottom 4
    Dark Green, Red, Purple, empty


    I pulled a perfect, non rotted complete vac system,
    from my 81 Lebaron parts car.
    I use it as a reference for the other Ms.
    I followed this for my 88 Diplomat AHB and everything works as it should.
    Vac Diagram.jpg
     
    Ruby and rcmaniac791 like this.
  3. Dr Lebaron

    Dr Lebaron Well-Known Member

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    Marty-
    3847622 is the part you need. A/C vacuum hose and connector

    includes both connectors (one at each end)

    I have it www.arizonaparts.com
     
  4. rcmaniac791

    rcmaniac791 Well-Known Member

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    This is just what I needed. Thank you!
     
  5. Rustyroger

    Rustyroger Well-Known Member

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    Subscribed so I can refer to the information here. :)

    Roger.
     
  6. Rustyroger

    Rustyroger Well-Known Member

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    My 1984 Fifth Avenue had no block connector at all, just seven vacuum line coming from the HVAC control. However thanks to the guys who contributed to this thread I got it figured out. :)
    All is still not well, I couldn't get the vents to stop blowing air in any position other than "OFF".
    So I checked out all the actuators and it turned out to be the bi-level & a-c/heat actuator is working, but the rod it operates is seized. I'm guessing it operates a door that opens and closes airflow to the vents?.
    I suspect the heater/a-c unit needs to come out to fix this, how big a job is this, or is there another way to approach the job?.

    Roger.
     
  7. Aspen500

    Aspen500 Well-Known Member

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    You are correct. The vacuum motor moves a door inside the plenum. IF your '84 is the same, or similar, to my '79 Aspen, that actuator attaches inside the plenum and it (the plenum)has to come out, then apart, to change the actuator. Should be on the left end of the plenum, near the throttle pedal. It's called the mode door actuator and switches between vents and heat/def.
    What you may want to do is, remove the nuts that hold the actuator on and see if you can pull it out. That would check if the door itself is stuck or the actuator is stuck.
    It is a big job to change. The HAVC plenum has to be removed from the car which isn't really a 10 minute job.
    If it is the actuator, the next hurdle is finding a replacement. I had a heck of a time finding a recirc door vacuum motor last year. Got it from Deconstructor Jim, who used to be on this site but stopped posting suddenly over a year ago, for some reason.
    If it turns out you need one, you can try him through his website.
    Jim's Az Parts
     
  8. Rustyroger

    Rustyroger Well-Known Member

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    Guess I'll have to bite the bullet and pull out the plenum. I already removed the screws holding the actuator, in my case it's outside the plenum, fairly easy to get to, and checked if it worked by removing and replacing the vacuum tube. the actuator itself is fine, as are all the others which is at least some good news, but the rod attached to the actuator won't move.
    Before I pull it all apart I'll try getting under the dash and trying to free the door, but hope for the best, prepare for the worst.....:rolleyes:
    Anyways, thanks for your quick reply.

    Roger.
     
    Last edited: Jan 15, 2019
  9. Rustyroger

    Rustyroger Well-Known Member

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    I managed to free off the door without taking the plenum out. I was able to remove the defroster ducts and air vents, which gave me access to top of the post the door pivots on, a little WD40 and jiggling the post with some vise grips freed it off. :D
    So I turned my attention to the heater blender, the door was also seized but after removing the motor I was able to free it off in the same way as the other door.
    But... the motor was also seized. Nothing to lose, I pried the cover off an found everything stuck solid. The motor wouldn't turn, the sprockets taking drive from the motor to the rotating head, the head itself, all seized. Normally I'd have said forget it, I'll get another one. But I want to put the interior back together as soon as possible, so an afternoon freeing off every moving part ensued. Still, I now have a functioning air blender system again.
    Then a trip to the local DIY store for some foam draught excluder so I can put the ducting back without any leaks.

    Roger.
     
  10. Rustyroger

    Rustyroger Well-Known Member

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    Looks like I was premature in saying I'd fixed the S.A.T.S. blend door motor, it quit a day later.
    Which leaves me with a problem; Does anyone have a working motor I can buy?, or would it be easier to fabricate a cable operation for it, which I understand non S.A.T.S. and non a/c cars have?.
    Bear in mind I can't go to the local pick'n'pull, the nearest junkyard likely to have one is a 6 hour flight away.

    Roger.
     
  11. BudW

    BudW Moderator Staff Member

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    The AC/Heating (HVAC) system used from ’76-79 (F and M-body) is completely different than the HVAC system used from ’80-89 (FMJ).

    Also, the no-A/C is completely different from A/C versions. I can’t comment about the differences between standard no-A/C versions vs Bi-Level no-A/C versions, for don’t think I recall working on a Bi-Level no-A/C system before. The no-A/C versions are not the issue at hand, here.

    Let’s try to avoid comparing ’76-79 HVAC versions to the ’80-89 versions. The firewall components and rearward are mostly different


    Next – that green vacuum hose block tends to crumble – even when cars were somewhat new. In early ‘80’s, the front wheel drive (FWD) cars got reformulated green plastic that holds up a lot better. I had a friend that had an ‘80’s Caravan and stole all the under-dash HVAC hoses and moved it to his Diplomat and it worked fine. I would think it might have needed some stretching (ie: hoses cut and lengthened) – but I didn’t ask any specific questions. For whatever reason, All FMJ’s got the crappy plastic 7-way vacuum connector that crumbles when someone blinks their eyes 10-feet away.

    Also, the ‘80’s Caravans use a 7-way vacuum hose extension that has the male and female 7-way connector (with the good green connectors) that if a person wanted to retain the “connection”, you can cut that foot-long extension in half, then use vacuum hose to splice both ends to your existing harness.

    Honestly – the easiest and best way, is to just clean off the “crumbled connector” parts from existing vacuum lines and use a short piece of rubber vacuum hose and splice the existing hoses, color to color, as mentioned above. Most of us will rarely need to disconnect your splice – and if you do, it’s not hard to get them back correct, again.


    ON A DIFFERENT NOTE: the two vacuum tubes that go through the firewall, the “black” and “gray” tubes, tend to break when man-handled. When this happens to the black tube, you will not have any vacuum to work any of the vacuum controls inside the cabin. The black tube connects to the vacuum tree on intake manifold. This is a picture from my ’86 Fifth Ave 318 2-bbl.
    20161201_125857r m.jpg

    If the gray tube cracks (or gets disconnected and not reconnected), then the hot water valve is inoperative. This is a picture from a fellow forum members car.
    20161106_161411 m.jpg
    The green circle is the hot water valve (used on A/C cars (either normal or SATC), only). The gray hose is marked by red arrows (for proper routing). There is a firewall grommet the gray and black hose share, is located in about the area of the orange circle.
    I would guess that most of our members street driven cars – either or both hoses have at least one crack in the plastic tube(s) – but it is easy to fix using a short piece of vacuum hose (might have to take a piece of tube to auto parts store to get correct size).

    Generally, the underhood tubes and the green 7-way connector is where 99.5% of all A/C vacuum related problems are at. The other vacuum components do not five much problems, in my opinion.



    The SATC motor hasn’t been available from Chrysler for a long time and I hadn’t found anyone who fixes them. I have (or had) a box of about 15 bad SATC motors, in hopes of fixing a few of ‘em – but hadn’t seen or ran across that box in a long time.

    In my opinion, if you have an inoperative SATC system, the best fix is to change it over to a conventional A/C system. The two A/C control heads are slightly different (conventional uses a cable that connects to the top A/C lever, whereas SATC uses an electrical sensor connected to the control head lever) – but it is not hard to obtain an older control head (or get one from a ‘80’s Dodge pickup, etc.) or get a lever and change your SATC control head over.

    I couldn’t find much online for decent photos (garage is still in a deep-freeze), but these will work (swiped from internet).
    3603206 74-6 ATC control hd.jpg
    This is an ATC (full-automatic, not semi-automatic that our cars have) used on mid ‘70’s full size Chryslers – but it is almost the same as the SATC heads M & J’s use (this version has no blower speed control). The temperature control lever (I outlined in white to make it more visible) is different. To change levers, you need to push down on and then sideways to release the clip (blue arrow), and the lever comes off. The electrical position sensor (yellow arrow) can either be removed or left in place if you so desire.
    3846338 Temp Dr Lvr.jpg
    This is what a conventional temperature lever looks like. There is a tang for a cable loop to go around. The cables used in the late ‘70’s and ‘80’s have quick-disconnect clips on them that look like this:
    91 PU Control Hd b.jpg

    iuREEBGH2F.jpg

    dscf7464.jpg
    All the ones I’ve seen are red. The control head base has a quick disconnect socket for cable already made on. Note: those red cable clips have been sturdy, but I’ve noticed as they get older, they can break – so just push enough to disconnect the clip. That said, if cable clip(s) do break, keeping the cables in place with a zip-tie is an easy fix.

    I have heard (but not yet verified) that temperature control cables from early ‘80’s pickups and full-size vans will work – but will be a tad long. It is much better for a cable to be “too long” than “too short”.

    The rod coming out of evaporator case – which the servo motor turns will work with a cable. The rod (is actually called the blend air door or temperature control door) is threaded and cut so it has a “D” shape to it. It uses a standard SAE nut to hold the lever in place (not sure of size, right off). The lever can be made – but the lever is the same one Chrysler has used on most all vehicles in ‘70’s and ‘80’s. I have one that I installed into my ’86 Fifth Ave to convert it to conventional A/C already, and there is a small chance I took pictures of what it looked like (if pictures didn’t get eaten by a recently died hard drive).

    The lever is about 3 inch by 1 inch (75 x 25 mm) with a stud on one end for cable adjuster clip to slide onto (maybe ¼” diameter (6.3 mm) possibly – going by memory).

    A person can take a normal sleeved cable and modify it to fit, just as easy (in place of an official cable). Having one of these adjustable clips should make one end easier (see picture, above, with yellow clip). That adjustable clip can be obtained separately.

    After the cable changeover, the remaining SATC wiring harness (which is separate from other dash harnesses), the aspirator and evaporator temp sensors can be removed or left in place if one desired.
    BudW
     
  12. Ruby

    Ruby Member

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    Thank you for posting this diagram! I now have a working heater controls..