1978 eldorado air ride ?
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The Classic Cadillac Forum Discussion, 1978 eldorado air ride ? in Past Cadillac Vehicle Discussion; Hello, Its been a while since I purchased my 1978 Eldorado biarritz, I was not really too concerned with the ...
  1. #1
    unautherized is offline Cadillac Owners Member
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    1978 eldorado air ride ?

    Hello, Its been a while since I purchased my 1978 Eldorado biarritz, I was not really too concerned with the air ride since first I don't drive it much at all, but I noticed wheel hop in the back when I hit a series of bumps. I also thinks the car sits a little high in front,or low in back. Today I removed the compressor from the car and tested it on the bench. there is a terminal with a green wire going to it and if I hook it up to power it will run. what I was wondering is if there is anyone here who might enlighten me of what might be the most likely cause for no power making it to the motor. and what do the other two wires that are plugged into the compressor do? blue and white. Everything looks physically un altered and complete. I was wondering at first if maybe someone disconnected it purposely ? Any way Is it a fairly simple system?, any usual typical problems I should look for? Do these cars normally sit lower in the back without the air shocks working? Is it probably the reason for the wheel hop? thanks in advance Rich

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  3. #2
    MrCads is offline Cadillac Owners Member
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    Re: 1978 eldorado air ride ?

    Give me some time and I will check the manual. It seems to be a PITA system. The car sits down after a while, but as soon as you turn on the ignition, the compressor should start running and pump up the shocks some. Then, based on the load in the car, the system should adjust the pressure accordingly.

  4. #3
    CADforce69 is offline Cadillac Owners Connoisseur
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    Re: 1978 eldorado air ride ?

    These systems are automatic so they should work always when ignition is on. There is a lever sensor near the rear axle; when it touches body floor it closes the circuit and compressor works; when it reaches some height, sensor doesn´t touch floor anymore so circuit opens and compressor stops working. Have you checked if the fuse is blown?

  5. #4
    unautherized is offline Cadillac Owners Member
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    Re: 1978 eldorado air ride ?

    Well,, Thanks here is an update, I am perplexed, First I go under the car and find the leveling sensor, I find that it appears as though a little set pin is missing on the shaft, Yay, I see the shaft is not really moving with the lever (slipping) so I'm happy, it looks like I found a problem. While under the car with the ignition on I test for any kind of power at the plug terminals to ground. When I touch one of the wires to ground with a test light I hear the compressor run for a second. So I plug in the sensor box and move the lever up and down manually and nothing happens, so I take the sensor apart to find it is not mechanical so much as a solid state thing inside that apparently makes and brakes a field between 4 posts with the use of a plastic wheel with tabs on it, and must make or break current to the needed wires to make things work. So I put every thing back together and as I am plugging the wire plug back onto the the sensor the compressor makes a clicking noise. along with the clicking noise I find that if I continue connecting and disconnecting the plug , each time I plug it in the compressor will run for a second.
    I took the compressor back out and have it on the bench again. There is a ground wire (black), A green wire that goes to a post on the motor and a plug near the head of the compressor that has a white and blue wire. When the key is on the blue wire is hot, If i plug and unplug it the motor will run for a second. On the bench however, you cannot get anything to happen by powering the ground and blue wire ??? yet if you power ground and the green wire on the motor it will run fine for as long as you power it.
    I know this is a long line of info so appreciate anyone who made it past the first two sentences, But maybe someone knows enough about this to understand. there is obviously some indirect events,switches, I Dunno. I have a very mechanical mind and can usually figure things out but like I said Perplexed for me is the word of the day,,,, But I can pass the bad fuse and other possibilities so that you who might be able to help have more info,, Thanks for sticking with my long post. Rich

  6. #5
    unautherized is offline Cadillac Owners Member
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    Re: 1978 eldorado air ride ?

    Ok, Update, thanks MrCads for the very helpful literature on trouble shooting and function, After some testing as per the paperwork I believe I need a leveling sensor. Because I can make the compressor run from the back by bypassing things and crossing wires as explained in the papers.
    Something I don't understand is why I have continuity between the power terminal on the compressor and ground,, If I tested by jumping wires near the relay under the dash as explained in the paperwork I blew the fuse, which led me to believe there was a short in the compressor. But if I test things from the back everything works. Well I'm sore and tired now so I'll clean up and put things back together and call it a day and hope to find a level sensor to try. Thanks again for the help.
    I just wonder if anyone could explain why I would have a continuity reading from the green power terminal on the pump motor and ground, That doesn't make sense to me.

  7. #6
    MrCads is offline Cadillac Owners Member
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    Re: 1978 eldorado air ride ?

    Quote Originally Posted by unautherized View Post
    Ok, Update, thanks MrCads for the very helpful literature on trouble shooting and function, After some testing as per the paperwork I believe I need a leveling sensor. Because I can make the compressor run from the back by bypassing things and crossing wires as explained in the papers.
    Something I don't understand is why I have continuity between the power terminal on the compressor and ground,, If I tested by jumping wires near the relay under the dash as explained in the paperwork I blew the fuse, which led me to believe there was a short in the compressor. But if I test things from the back everything works. Well I'm sore and tired now so I'll clean up and put things back together and call it a day and hope to find a level sensor to try. Thanks again for the help.
    I just wonder if anyone could explain why I would have a continuity reading from the green power terminal on the pump motor and ground, That doesn't make sense to me.
    That sucks! I have a few more pages of diagnostics for the ELC. I'll get them to you tonight.

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    unautherized is offline Cadillac Owners Member
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    Re: 1978 eldorado air ride ?

    Well In the process of trying to figure out the air level system I found that I was able to manually power up the compressor and the car sits much better, doesn't look like my Uncle Bobby has a body in the trunk now,, I went for a ride and it feels better, But But But But ,,, Now the radio and or antenna wont work, worked yesterday and the fuse looks OK, So it looks like I will be chasing my cadillac tail for a while.
    Attached Images
    70eldo and talismandave like this.

  9. #8
    unautherized is offline Cadillac Owners Member
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    Re: 1978 eldorado air ride ?

    MrCads, although the info you sent me is worth its weight in gold, Without it I may as well have been trying to figure out if the light in the fridge was going out when I close the door,LOL.
    The problem I had was that there is a specific sequence of events in the testing process and as would always be the case for me the first test was did the compressor run or not when key was turned on, Well it would run for a second or less, and shut off. ( sometimes) So that kind of threw me for a loop in the sequence process, but I do understand things better, and its truly valuable info.The fact that everything works as it should, ( Besides the radio) with the ride level if tests are done from the back at the level control. I think thats where the problem is. I wonder though as I said earlier in the post,, the set screw was not on the axel of the level control. I wonder how did they orient the lever as a starting point, because there are plastic walls that apparently make and brake some kind of field inside the sensor, I wonder if its just not in the correct place? there is a line marked on the end of the axel. But I don't know where it should be positioned, I just installed a set screw where I saw what appeared to be a mark on the shaft from a past screw. Anyway this is maybe more info than most care to hear. and thats if anyone understands my text. Anyone want to buy a pretty eldo with minor issues? LOL

  10. #9
    carnut is offline Cadillac Owners Master
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    Re: 1978 eldorado air ride ?

    With the key on and the level sensor arm disconnected from the rear axle, the underhood pump should start pumping after 15 to 20 seconds if you push the arm up towards the belly of the car. You should see the rear of the car raise. Assuming all the lines dont leak and the rubber bags on the rear shocks arent cracked, it should hold height most all the time. The shocks require a minimum of 20 lb. All the time to keep the car somewhat level. If there are leaks, the pump will turn on too often. Most people push the rear sensor arm up and expect an immediate reaction from the pump. There is a built in 15 to 20 second delay so as to not overheat the pump. The arm on the height sensor should have an elongaged hole under one screw. You can set ride height by loosening that screw and altering the arm in relation to the link that attaches to the rear axle. The link that goes to the rear axle is rarely if ever adjusted, the arm on the sensor is your adjustment.[COLOR="Silver"] Nice car by the way! Had a 78 triple yellow for awhile. Regarding the radio, check all the fuses with a test light. There are normally 2 radio fuses. One constant to hold memory of stations and another that's a switched power to turn on the radio. 20 amp if memory serves.

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  11. #10
    unautherized is offline Cadillac Owners Member
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    Re: 1978 eldorado air ride ?

    Thanks for the input, Now that I have been through the system with much needed info on trouble shooting and operation,, I can try to clean up my post ( so its a little less like Who's on 1st and whats on 2nd ) so that if there is someone out here that knows these systems well they might chime in.
    1) Probably significant info to someone who really is deeply familiar with the system,,,,,,And not mentioned in the service manual.
    If you turn the key to the on position, the compressor runs for a second (with the car low and shocks empty) with each on / off click of the key it will do the same, (won't continue to run)
    2) If I run power from the +battery to the compressor motor terminal the compressor will run.
    3) If I run power to the exhaust valve on the compressor it will exhaust.
    4) If I bench test the relay from under the dash it works, powers and makes contacts
    5) If I check everything from the back at the level sensor as per the manual,, Power at two points, Yes, this to ground motor runs ,, Yes . cross these two motor runs,, Yes.
    So basically all individual components seem to work with the exception of the level sensor because its much harder to test, (specially since I don't know if the shaft is in the right position because the set screw was missing.)
    I did try since everything else works to put everything together and try moving the level sensor arm to many different places with no results.

    As it stands right now I can run the compressor manually with power and lift the rear, then if I start the car it will exhaust the air (with the sensor arm in any position) so if I want to keep the air I have to unplug the level sensor.
    My personal conclusion now that I have been enlightened by members here on operation, and have a pretty good understanding of how everything is supposed to work, Is that the level sensor might be the problem.

    Aside from that is the fact that the manual during the check out procedure had me (With key on) and (with relay in place) connect the blue wire to ground and see if the compressor runs.
    Well that was when I blew two fuses, radio 7.5 amp and antenna 20 amp.
    2 things I don't understand 1) after the fact it looks like they had me short out a live wire, unless I am not understanding the text. 2) why did the radio fuse blow if it says in the book clearly that the circuit comes off the turn signals.
    I replaced the radio fuses, took the car for a ride and about a half mile up the road the fuse blew,, I got to my destination and replaced the fuse and unplugged the level sensor and the radio is fine now.
    So, Did I manage to "clean up my post" LOL
    Is this a place for things that are "fun" ,LOL, I will apologize for my lengthy posts ahead of time, Its just that I think if all the info is given clearly ( I Hope) there is a better chance someone who has dealt with a similar thing might figure it out confirm my thoughts.
    Level sensor??
    Did I misunderstand the Blue wire to ground like it said in the book???
    Where might I look for a replacement level sensor????
    Why would the radio fuse have anything to do with the air ride???? Thanks, Rich
    )

  12. #11
    MJDART's Avatar
    MJDART is offline Cadillac Owners Enthusiast
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    Re: 1978 eldorado air ride ?

    Really nice Biarritz by the way!!! My mom bought a new one in 77 and I got to drive it home from the dealer - awesome vehicle. I was posting because my 2006 had NoviMat shocks that are really brilliant in the design they self level. If you can't get the old system to function you may want to look into these. I would put 10 bags of mulch in the trunk and with in a block or two they would self level.

  13. #12
    70eldo's Avatar
    70eldo is offline Cadillac Owners Connoisseur
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    Re: 1978 eldorado air ride ?

    Maybe Cadillac Tim can recondition your ALC switch? http://cadillactim.com/page4.html

    H
    ere's someone else working on a 1978 Eldorado ALC: http://forums.cadillaclasalleclub.org/index.php?topic=113570.0

    T
    his might be a new replacement part at RockAuto? http://www.rockauto.com/catalog/more...922&cc=1025930 /

    http://www.rockauto.co.uk/catalog/x,carcode,1025930,parttype,3048

  14. #13
    unautherized is offline Cadillac Owners Member
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    Re: 1978 eldorado air ride ?

    Thank You,, This Is another batch of very helpful info, Could only happen to me that the very issue I had on my car would bring me to a misprinted service manual, ( Standard Of The World?) I guess this one had my name on it.
    At least I understand things better, Maybe the manual is wrong about the power source for the leveling system coming from the signal circuit too.
    Any info on how the level sensor was originally placed on the car when assembled?
    The plastic axle coming out has a line on one side of the face of it and the box has a small indent on the end, I am assuming this had something to do with setting it up when new, all the manual says is that you note the position when removing it and put it back the same. Well what if it didn't have a set screw in it and you don't know where it was. any deeper info on how to test the level sensor??
    Thanks again very much all these puzzle pcs will get me where I need to be. Rich

  15. #14
    MrCads is offline Cadillac Owners Member
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    Re: 1978 eldorado air ride ?

    Quote Originally Posted by MJDART View Post
    Really nice Biarritz by the way!!! My mom bought a new one in 77 and I got to drive it home from the dealer - awesome vehicle. I was posting because my 2006 had NoviMat shocks that are really brilliant in the design they self level. If you can't get the old system to function you may want to look into these. I would put 10 bags of mulch in the trunk and with in a block or two they would self level.
    Hmmm...interesting. I was just looking at the Nivomat, but I cannot find anything for a 77 Caddy.

  16. #15
    unautherized is offline Cadillac Owners Member
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    Re: 1978 eldorado air ride ?

    Well, I am pretty certain that I will need to find a level sensor for my car, If anyone has or knows where I might find one I would appreciate any input, while I keep checking Ebay etc.
    I wonder if anyone here has ever installed regular rear air shocks, and if so how they worked. It may be a long time before I find a sensor, I will likely try to sell the car in the near future, I hardly drive it at all.
    I was thinking that this was a pretty ridiculous set up anyway,and if I package all the original shocks and parts and keep them with the car. It might be considered a bonus to some. I'm thinking with the weight of the car that regular air shocks should ride pretty well, if not the same as whats in there. Anyone ever tried this ?? It is a beautiful low mile example and so I don't want to botch things up on it, but I think this might be considered an improvement. What do you think?

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