AC power problem

Interior and Electrical

  1. SharkHead

    SharkHead Member

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    1989 Chrysler Fifth Avenue M body, the air was working fine, the clutch engaged perfectly, however the vacuum for the controller was not hooked up so it blew out the bottom vents. When I hooked up the vacuum for the controller suddenly there is no electrical power on the system anywhere, (coincidence?)-the air blows out the proper vents but there is no power for the AC clutch, I jumped the low pressure switch to no avail ( there is also no power coming into the low pressure switch) and checked the under-dash fuse, also checked the plugs on the back of the controller everything looks okay, where do I go from here?
     
  2. BudW

    BudW Moderator Staff Member

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    I don't think the two issues are related, unless something got shorted (and blew a fuse) while you were checking on hoses.
    Do you have access to a FSM (Factory Service Manual)?

    The first thing I would check is your fuses.
    #2 (20 amp yellow) is for A/C clutch.
    #4 (30 amp lt. Green) is for rest of A/C system.

    These are copies of a copy, which were copied from the FSM. Not the best but should get you pointed in the right direction.
    BudW
     
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  3. SharkHead

    SharkHead Member

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    Thx BudW! I did not realize that there are two fuses on the AC system, I had checked the 30 amp green one, I will certainly check the 20 amp yellow one tomorrow, was there supposed to be an attachment with this message?
     
  4. BudW

    BudW Moderator Staff Member

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    Um, yes. It must be time fer bed . . .
    Annotation 2020-04-22 185937.jpg

    Annotation 2020-04-22 190022.jpg
     
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  5. SharkHead

    SharkHead Member

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    Got it, the single power wire on the back of the controller had become unplugged! The air volume on the vents is ok but not great-any suggestions to increase volume?
     
  6. Mikes5thAve

    Mikes5thAve Well-Known Member

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    Is the vent door working properly and diverting all the air to the right spot? Did you notice if the vacuum connection to the heater switches is still all together? Both those will affect how much air comes out. Do all the fan speeds work?
     
  7. SharkHead

    SharkHead Member

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    All fan speeds work-the vacuum to the heat side IS NOT hooked up-previous owner completely disconnected the heat System, including bypassing the heat water hoses, the vacuum is sticking out of The Grommet on the firewall inside the engine compartment but is hooked to nothing
     
  8. Addy87

    Addy87 Member

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    There's also a vacuum hose connection assembly (clear plastic hoses, IIRC) that hook up right behind the push-pull switch assembly in the dash. The connector on my '87 Fifth Avenue broke years ago and I replaced that hose connection assembly with the MoPar dealer replacement assembly as there wasn't much air coming out of the vents, especially when driving up a hill. Replacing that help some, but not completely. Found that there was a TSB about the loss of vacuum when going up hills etc. and ended up putting a dash pot in one of the vacuum lines under the dash and that fixed the problem. Since I did that years ago don't remember where I hooked up the dash pot (universal one available at parts store). Am unable to check now since I have a replacement knee. Is the hot water valve (for the heater under the hood) working as well?
     
  9. SharkHead

    SharkHead Member

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    I think I have everything working correctly, all the vacuum is hooked up, one question however, I did need a new heater control valve because the old one which was original was not stopping the water flow, however all the hoses were cut and disconnected by the previous owner so I'm not positive of the water direction flow, can someone describe which hose is the water flowing out from the engine towards the heater core which I assume is also the hose in which the heater control valve should be inserted- see attached photo, is the water that goes to the heater core the hose marked in red which originates basically at the water pump or the hose Marked in blue which originates in the water jacket on top of the manifold near the carburetor?

    Message_1587839866897~2.jpg
     
  10. BudW

    BudW Moderator Staff Member

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    Here is a couple pictures from my '77 FSM (Factory Service Manual). Note: '80 and newer use 5/8” heater hose for both directions – but routing and layout is the same.
    77 FSM pg 24-06b.png
    no A/C vehicle (above).
    With A/C vehicle (below).
    77 FSM pg 24-53d.png

    To answer your question, the hose marked blue is Hot going towards heater core.

    The hose marked in blue, is also a tad bit too long – but better for hose to be too long than too short.

    Here are some pictures from my '86 Fifth Ave showing proper routing:
    20200501_132233.jpg
    20200501_132144r.jpg
    20200501_132212r.jpg
    BudW
     
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  11. Mikes5thAve

    Mikes5thAve Well-Known Member

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    Side note, BudW's has an aftermarket valve.
    The original setup has the same hose routing but the hose without the valve is the one that clips into the bracket.
     
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  12. Justwondering

    Justwondering Well-Known Member

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    Bud ... its always such a pleasure to look at engine wires that haven't ever been rat chewed.

    What is a dash pot?
    I checked the interweb and it looks like its a simple mechanical device.
    Is it sorta like a check valve ? How does it 'add' to the air flow for the AC?

    JW
     
  13. BudW

    BudW Moderator Staff Member

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    Can you take my picture (or your picture) and draw an arrow to what you are asking about, please?
    BudW
     
  14. Justwondering

    Justwondering Well-Known Member

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    In this thread its mentioned in #8 reply above, about 2/3 the way down in the paragraph.

    I just used the words 'dash pot' in a search term and found several examples and a wikipedia reference -- none for an a/c though.

    JW
     
  15. BudW

    BudW Moderator Staff Member

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    OK, I'm up now. The word dashpot might not have been the best choice of words in this case.

    On some cars, the engine vacuum level drops when going up hills, accelerating or passing cars (think two-lane passing) and what happens is there is not enough vacuum supply to keep the A/C vacuum doors open.

    There is actually two fixes:
    One is to insert a vacuum restrictor (orifice) into the vacuum source hose, which is what is being referred here. These come in many shapes and the ones made 30 years ago are maybe three times larger than these examples. The color points to the size of the orifice inside.
    Vacuum Orifice.jpg

    The other fix is to install a vacuum canister. This one is from '68-70 B-bodies. It looks like a large repurposed vegetable can (~6" by 6") with a welded-on mounting bracket, and this one has a two vacuum hose fittings. Behind the hose fittings is a one-way check valve. This is the best fix – but is also the most expensive.
    Vacuum Canister.jpg
    I have one (still in my garage) from my '68 Charger – but it is two (or maybe three) times larger sense it had vacuum operated headlight doors.

    This is what Chrysler used starting in the early '70's – which I refer to as the vacuum ball (it looks like a ball with a mounting bracket). This version is still being made by Dorman (I think). It is about 6" in diameter (I think).
    Vacuum Ball.jpg

    What is interesting is my '97 Dodge diesel pickup (and possibly some of your diesel pickups) still uses vacuum A/C controls and vacuum doors - in many cases much like your Fifth Ave. Diesels do not make engine vacuum – so to operate the A/C and power brakes, Dodge installed an small mechanical vacuum pump to operate these items. A simple system and much less complex than electric A/C doors and hydroboost for the power brakes.
    The mechanical vacuum pumps look somewhat like a mechanical fuel pump (work off of the same principal).
    Mechanical Vacuum Pump.jpg


    Getting back to basics. Vacuum is simple and mostly trouble free. It does suffer from vacuum leaks (the plastic pipe/hose tends to crack/break/leak. Vacuum hose is better but more expensive. It tends to get damaged from oil (oil and rubber don't mix well).

    High performance engines and diesels toss a curve ball into the vacuum supply and need a separate pump to get things done. There are a couple of common inexpensive 12 volt vacuum on used nowadays to replace the gasoline engine source for those guys. One of many examples are:
    GM Electric Vacuum Pump.jpg
    If considering one, I'd recommend going to a Pull-a-Part and get it. and the pigtail, for (maybe) $10.

    JW, did this help you any?
    BudW
     
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  16. Justwondering

    Justwondering Well-Known Member

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    Excellent - as always.
    Basically, (for this thread), its an assist for the vacuum line to keep the AC vacuum line needs addressed. Several ways to accomplish it (additional reservoir up to separate vacuum generation) depending on circumstances and budget.

    I'll go look in the engine bays tomorrow and compare the fifth avenue to the diesel and the suburban. Slowly this is all starting to make sense.

    JW