functional principle of air suspension [solved]

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functional principle of air suspension [solved]

Postby 5151 mm » Sat Mar 12, 2011 5:50 pm

1.) What has to happen that the control unit switches from "filling the rear air bags with new air" to "filling the front air bags with new air"?
2.) How do I fill all 4 air bags with an external compressor? (System switch ON / OFF? All valves open? Ignition ON / OFF?)
3.) How do I see, whether the system already has opened the valves of the front air bags?
4.) What could be a reason that the system doesn't open the front valves (but the rear ones)?


Problem: Front solenoids won't get opened.
Problem solved (see page 2, post 4).
Last edited by 5151 mm on Mon Mar 28, 2011 4:51 pm, edited 1 time in total.
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Re: functional principle of air suspension

Postby K MANIAC » Sat Mar 12, 2011 8:08 pm

5151 mm wrote:1.) What has to happen that the control unit switches from "filling the rear air bags with new air" to "filling the front air bags with new air"?


You first need to fully understand how the air suspension system works.

The air suspension system consists of four springs, four solenoids (the air inlet and exhaust valves on each spring), three height sensors (one for each front spring and one for both rear springs), the air tubes to each spring, the dryer, the compressor, the control unit, the on/off switch, and the "check suspension" light.

When the system and the ignition key are turned ON, the computer looks for signals from the three air sensors. Typically car starts out a level trim empty as it corrected itself after the last time it was driven. When you, your passengers, and any luggage are placed inside the car, the springs will compress with the added weight before you turn the key. The lowering of the car from the added weight also compresses the three height sensors to the point that all three tell the control unit that the springs need air. Once the ignition is turned ON, and the control unit sees a need for air at all four wheels, it will first turn on the compressor and simultaneously open BOTH rear solenoids, first. Once the rear height sensor reaches the proper trim height, the control unit will close BOTH rear solenoids and simultaneously open either one or both of the front soleniods, one if only one front height sensor reports low, or both if both height sensors report low. Each front solenoid will stay open until each respective front height sensor comes to trim height. Then the control unit will close the respective front sensors and shut off the compressor once both front sensors are at trim level together. The car will remain at trim level and make any minor corrections as you drive. When you arrive at your destination and turn off the ignition, the car will be at trim level. But as soon as you and your passengers get out and take your luggage with you, the car will rise in reaction to the loss of load. The air suspension control unit remains active for a period of time after turning off the ignition. When the three wheel sensors tell the control unit that the car is too high, the control unit will first open both rear solenoids and the vent valve in the compressor unit simultaneously. The air will expell through the open solenoids, respective air tubes, dryer, and out the vent valve as the car lowers. Once the rear sensor reaches trim height, both rear solenoids close and the front solenoids open to vent the front springs. Once each respective front height sensor reaches trim height, the respective solenoid closes and the vent valve will close once all sensors reach trim height.

Now there is a reason why the air suspension system fills only two springs at a time. The front springs support the full weight of the engine and all the other stuff bolted in the engine compartment. The rear springs, however, support an empty body shell and sometimes rear passengers and luggage if present, but not all the time. As a result, the front springs take more air pressure to fill than the rear springs. When at trim level, the air pressure inside the front air springs is much greater than the air pressure inside the rear springs. All four air tubes connect to the top of the dryer without any valving. Whenever the compressor is working, all four air tubes receive the same air pressure inside them all the way to the solenoids, but air only flows through the tubes where the solenoids are open. If for some reason, the two rear solenoids were leaking air from their respective air tubes into the rear springs while the front solenoids were open in an attempt to fill the front springs, the higher pressure air in the front springs will push back against the compressor and the rear springs will overfill with air. The fronts springs would drop to the ground as a result and your car would look something like this...
Image

5151 mm wrote:2.) How do I fill all 4 air bags with an external compressor? (System switch ON / OFF? All valves open? Ignition ON / OFF?)


In order to use an external compressor to HELP fill the air springs, the system switch needs to be ON and the ignition switch need to be ON, as well. Otherwise you will be pumping air up against closed solenoid valve and the only place left for that air to go is out through the o-ring seals on top of the dryer and at each air tube connection at each solenoid.

5151 mm wrote:3.) How do I see, whether the system already has opened the valves of the front air bags?


The solenoids make a destictive "click" when they open and close. You need to listen carefully for these clicks as the system fills. Having more than two ears in attendance is helpful for this task.

5151 mm wrote:4.) What could be a reason that the system doesn't open the front valves (but the rear ones)?


The only functional reason I could see for the system holding open the rear solenoids and not allowing the front solenoids to open would be if the rear height sensor was not telling the control unit that it reached trim level. This could happen if the rear height sensor was somehow disconnected from it's mounting points or if it was malfunctioning electrically.

Now that I have answered your questions, I now have a hunch as to why you asked these specific questions and what you might be experiencing with your car. Correct me if I am wrong, but is you car looking like THIS when you try to fill the air suspension?
Image
Seeing your car looking this way, it is easy to think that somehow the rear spring solenoids are staying open when they are not suppose to AND the front solenoids are not opening at all. That was NOT the case with my Continental and possibly not the case with our car either. My Continental got this way because of MOISTURE inside the air suspension system. There was so much water inside that the dryer beads (that are supposed to absorp water) were wet to the touch AND I had STANDING WATER that I actually poured out of my air springs once I removed them from the car. What I discovered, too, is that moisture and dust inside the system can cause the solenoid valves not to seal, making the system try (unsuccessfully) to fill ALL FOUR springs at the same time.
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Re: functional principle of air suspension

Postby 5151 mm » Sun Mar 13, 2011 4:18 am

Thanks for the write-up, dude!

The rear height sensor is at highest position. The front ones, too.
The compressor easily does fill the rear bags: The rear passenger side upper wheel well is 30 inch away from ground. The rear driver side upper wheel well is 2 inches lower (28 inch above ground). No one sitting in car. Gasoline tank is fully loaded. In the trunk, above the rear axle, is about 250 lbs of weight, due to LPG-gas system.
The rear rises with out a problem (very fast). I don't know whether it actually reaches the level that really is supposed for the highest height sensor position >> 30 inch?
But then: The compressor still runs, but the rear doesn't get any higher anymore than 30 inch / 28 inch. I noticed no "click" that would inidcate that the system is now pumping air into the front bags. And absolutely nothing changes in the front. Front is very low and doesn't rise at all. 26 inch front passenger side; 23 inch front driver side.

Is it possible, that the rear is still not at the wanted level and the system is trying to rise the rear continuously (but rear is to heavy?!) until the timeout comes and compressor shuts off itselfe, without even trying to rise the front?


We also have leaking air where the airtubes meet the dryer.
We are trying to fix the leaks.

I may try to remove one air tube from the dryer and put some air from an external compressor directly in the tube, just to see whether the front solenoids are dirty or still closed for some reasons.

As soon as I switch the suspension switch OFF, the rear deflates completely "down to the ground". The front doesn't do anything!!! But it seems like the rear is even a little bit lower than the front, which is like frozen in its position.
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Re: functional principle of air suspension

Postby K MANIAC » Sun Mar 13, 2011 10:14 am

Tell me a little more about YOUR suspension. Does it consist of all the original components installed at the factory over 20 years ago? Or, to your knowledge, have any of the pieces (springs, solenoids, , sensors, compressor/dryer) ever been replaced in the past? From what you describe to me, the suspension is acting the same way the suspension in my Continental was acting right after I got it, with a 24 year old suspension system that had never been serviced, and consisting of all original parts.

5151 mm wrote:The rear height sensor is at highest position. The front ones, too. The compressor easily does fill the rear bags: The rear passenger side upper wheel well is 30 inch away from ground. The rear driver side upper wheel well is 2 inches lower (28 inch above ground). No one sitting in car. Gasoline tank is fully loaded. In the trunk, above the rear axle, is about 250 lbs of weight, due to LPG-gas system. The rear rises with out a problem (very fast). I don't know whether it actually reaches the level that really is supposed for the highest height sensor position >> 30 inch? But then: The compressor still runs, but the rear doesn't get any higher anymore than 30 inch / 28 inch. I noticed no "click" that would inidcate that the system is now pumping air into the front bags. And absolutely nothing changes in the front. Front is very low and doesn't rise at all. 26 inch front passenger side; 23 inch front driver side. Is it possible, that the rear is still not at the wanted level and the system is trying to rise the rear continuously (but rear is to heavy?!) until the timeout comes and compressor shuts off itselfe, without even trying to rise the front?

Like I said before, the system cannot fill all four springs at the same time because it takes more air pressure to fill the front springs than it does to fill the rear. You seem to think that the rear solenoids never close and the front solenoids never open, causing this condition. Maybe that's true, but then again, maybe not. What I tried to point out before is that if the rear solenoids are TRYING TO CLOSE mechanically, but are not SEALING AIR TIGHT, AND the front solenoids are OPEN, the suspension will react in the SAME WAY, with the rears overfull and the fronts flat. My Continental did the same thing due to moisture in the original system. Maybe your car is doing the same thing as my Continental did for the same reason. I would expect that if all your components are original.

5151 mm wrote:We also have leaking air where the airtubes meet the dryer. We are trying to fix the leaks.

Contrary to popular belief, the air tube connections at the top of the dryer and at each solenoid are designed to pass air when the system is pressurized. Or in other words, and pardon the emphasis, THEY ARE SUPPOSE TO LEAK AIR AND ARE NOT SUPPOSE TO BE "AIR-TIGHT". The amount of air leaking through these connnections increases as the air pressure in the system increases. These eight tube connections act as pressure relief valves. The fact that the rear of your car rises at all tells me that the air tube seals are working as designed. If there were excessive or abnormal amounts of air passing through these connections, the car would NEVER RISE. Likewise, if all of these eight connections were truly air tight, or made air tight, you could overfill an air spring until it "pops" like a balloon, damaging something (like the car) or someone (maybe YOU). Leave these connections alone, and don't try to fix what ain't broken.

5151 mm wrote:I may try to remove one air tube from the dryer and put some air from an external compressor directly in the tube, just to see whether the front solenoids are dirty or still closed for some reasons.

Don't try this. It will not work and you will most likely break something in the process.

5151 mm wrote:As soon as I switch the suspension switch OFF, the rear deflates completely "down to the ground". The front doesn't do anything!!! But it seems like the rear is even a little bit lower than the front, which is like frozen in its position.

This is what I would expect if your rear solenoids are not sealing "air-tight". When this happens, the air in the rear springs is forced back into the air tubes by the weight of the car. Then, with the vent valve closed at the compressor, the only place left for that air to go, is to leak out through the "pressure relief valves", as known as the eight air tube seals, four on top of the dryer and one each at each solenoid. This is exactly what my Continental did before I serviced the air suspension.

At this point, I am convinced that you have a 20+ year old system, using original components, that has never been serviced AND is suffering from moisture contamination. The first thing that should be done is to service the dryer. Here is the link to the instructions.
http://thelincolnmarkviiclub.org/docume ... rDryer.pdf
I would expect that you will find moisture in the top of the dryer. You may even find corrosion on the big spring on the dry side of the beads. If this is the case, I would also expect pools of standing water in one or more of your air springs. The next thing I suggest doing is removing each air spring from the car. When you pull each solenoid from each spring, look at the valve seat on the solenoid. If it looks wet, replace it with a new solenoid. In fact, it might be prudent to just order four new solenoids before you start. Do not install new solenoids without baking the dryer beads first. Next, remove each spring, then turn it upside down to see if any water spills out. Also, inspect the outer surface of the springs for rubber deterioration. If you decide to reuse the spring, make sure it is dry inside before you reinstall. Let it bake in the sun or a warm, dry place. Otherwise, replace the spring. It would be good to install new o-rings on the tips of the solenoids where they mate with the spring.

Please let me know if you have any questions or comments.
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Re: functional principle of air suspension

Postby 5151 mm » Sun Mar 13, 2011 4:38 pm

Hi again :D
Thanks for your help!!

We didn't looked into the dryer yet...

Let me tell you something about our suspension.
All 4 air bags, the compressor and the dryer were purchased about 6 months ago (SUNCORE products).
All this was assambled to the car about 3 months ago.
The car is 21 years and one month old. For one year it is in our ownership.

Today we were able to decrease the leakage around the 4 air tubes on top of the dryer. Of course, there is still a very little bit of "leakage" - but as you said, this is supposed to be / this is normal. Cool. So we just solved one of the problems.

However, the front still won't rise. I also didn't even heard a "click" which would indicate a begun operation at the front.
So we just lifted a corner of the car and removed one front wheel (FR) to get better access to the components. We discovered a broken cable inside the wheel well. I think it was a yellow cable, but I'm not sure. This cable goes from the engine area to the electronic connector which goes to the solenoid of the air bag. The cable isn't cut, it just didn't have any insulation at this area anymore. We fixed the damaged cable. On the other front side (FL) we discovered exactly the same. Same-colored cable, same damage, same area. Fixed that, too.
I think this could be a reason why the front didn't rise. Maybe the bad cables caused short circuits and probably damaged the suspension control computer unit, which maybe doesn't serve the front at all anymore. Well, at least that's what I can imagine.

However, the front solenoids still won't opened.
So we disconnected the connector (the very same connector I just mentioned above - it is directly on top of the air bag and goes to the solenoid). On the cable, which goes back to the engine area, there is constantly about 12 V (hot at all times?!), but on the other hand there is for some reason no ground. That means the solenoid didn't get any ground. So we let the connector disconnected and took an external battery and put manually 12 V with + and - directly into the solenoid. Guess what, the solenoid finally opened! Cool! But you have to keep the external battery feeding the solenoid, otherwise the solenoid / vent (however you want to call it) will immediately close again. We just turned the ignition ON and let the compressor run and also let the one front solenoid open (feeded by the external battery). The compressor filled the rear and the one front corner all at once. But very slow. Very. The car raised, even the heavy front. We did the same with the other side's front solenoid. Finally the car is (manually) put in trim level. Nice! Finally some real ground clearance at all 4 corners!! Cool.


The main question is: Why does the front solenoids never get opened by the system?
Where do I find a wiring diagram?
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Re: functional principle of air suspension

Postby oldschool1 » Sun Mar 13, 2011 5:02 pm

5151 mm wrote:...

The main question is: Why does the front solenoids never get opened by the system?
Where do I find a wiring diagram?

In a closed, stock system, the front solenoids do NOT open until the rear sensor is first satisfied and then there is a LOW FRONT condition sensed by the front ride height sensors.

Return everything to thier original positions and start from there.
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Re: functional principle of air suspension

Postby 5151 mm » Sun Mar 13, 2011 5:12 pm

I can put the rear height sensor to a lower position to make it easier to satisfy the system.
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Re: functional principle of air suspension

Postby 5151 mm » Sun Mar 13, 2011 5:15 pm

When I push down the front with my body weight, while ignition ON, I can hear how the compressor starts to run. = The front sensor is sending a signal to the computer and to the compressor. But the compressor puts air into nothing, because the solenoids still keep closed.
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Re: functional principle of air suspension

Postby Mondragon » Sun Mar 13, 2011 9:10 pm

Might be a good idea to just replace the solenoids. unless there is a wireing problem not found yet. Have you tryed checking diffrent parts of the wire to see if there is a unseen break in them? if the sencer it sending a signal and the solenoid isnt getting one, the pump would just try and fill something that isnt open.
Kinda weared my drier does not leak any? I just put it on. I have no probs with bags over filling? my old drier leaked like crazy ended up putting another o ring on top of the stock one that fixed it till I bought my new one.
Also I replaced the shocks and struts they where toast and the springs where just fighting the shocks. Made it fill like a wooden wagon when I drove it.
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Re: functional principle of air suspension

Postby 5151 mm » Mon Mar 14, 2011 6:32 am

Solution still not found. I didn't worked any further on the car, yet.

Replacing solenoids? Why? All of them do work, just not automatically.
I checked the wires which were able to see and reach (which isn't much).
Do all the cables of the height sensors and solenoids end into the trunk to the suspension computer?
5151 mm wrote:Where do I find a wiring diagram?
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Re: functional principle of air suspension

Postby K MANIAC » Mon Mar 14, 2011 6:59 am

5151 mm wrote:Replacing solenoids? Why? All of them do work, just not automatically.

In order for a solenoid to function correctly, it must do TWO things; One - the valve must open when eletric power is applied. Two - the valve must seal air tight once it is closed.

Here are my questions for you: Have you removed each solenoid, applied 12-volt power to them and actually watched them open and close with your own eyes? And have you also tried to blow your own breath through them when they are supposed to be closed to make sure they don't leak?

One more thing about the air spring solenoids: Each solenoid is equipped with a diode. As a result, they are sensitive to electrical polarity. If you connect 12-volt power to them in reverse polarity [positive (+) lead to negative (-) terminal / ground (-) lead to positive (+) terminal], you will "fry" the internal electronics and the solenoid will cease to function.

5151 mm wrote:As soon as I switch the suspension switch OFF, the rear deflates completely "down to the ground".

As I said before in my earlier responses, your air suspension system will rise as you describe if both rear solenoids do not seal air tight when they are closed. Your statement above CONFIRMS what I just said. Turning off the air suspension system forces all four solenoids to stay "closed" and presumably "air-tight". There are only two things that would cause two fully inflated rear air springs to drop after the air suspension system is turned off. One - two faulty solenoids that are not sealing air tight. Two - two air springs that are leaking air, either through the o-ring seals between the solenoid and spring top on both springs or through a hole in both of the air spring bladders. Given both the way it rises AND the way it falls, I would put my money on leaking (not air tight) solenoid valves. I suggest you read about my experience with the air suspension system on my Continental for a little more background. viewtopic.php?f=61&t=3101

Below is the wiring schematic for the air suspension system from the 1989 EVTM.
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Re: functional principle of air suspension

Postby K MANIAC » Mon Mar 14, 2011 9:19 am

5151 mm wrote:Let me tell you something about our suspension.
All 4 air bags, the compressor and the dryer were purchased about 6 months ago (SUNCORE products).
All this was assambled to the car about 3 months ago.
The car is 21 years and one month old. For one year it is in our ownership.

This tells me that your springs should be good (no external leaks in the bladders), your compressor is strong and the dryer is dry (no need to rehab').

5151 mm wrote:However, the front still won't rise. I also didn't even heard a "click" which would indicate a begun operation at the front. So we just lifted a corner of the car and removed one front wheel (FR) to get better access to the components. We discovered a broken cable inside the wheel well. I think it was a yellow cable, but I'm not sure. This cable goes from the engine area to the electronic connector which goes to the solenoid of the air bag. The cable isn't cut, it just didn't have any insulation at this area anymore. We fixed the damaged cable. On the other front side (FL) we discovered exactly the same. Same-colored cable, same damage, same area. Fixed that, too. I think this could be a reason why the front didn't rise. Maybe the bad cables caused short circuits and probably damaged the suspension control computer unit, which maybe doesn't serve the front at all anymore. Well, at least that's what I can imagine.

The so-called cable to the solenoid contains two wires, the battery lead, a Black/Yellow stripe wire on both sides and the grounding lead back to the computer, Light Green/Orange stripe on the left side and Orange/Red stripe on the right side. If the insulation was worn off both of these wires, it is important that they be reinsulated separately. If these two wires are touching electrically, the solenoid will not open.

5151 mm wrote:So we disconnected the connector (the very same connector I just mentioned above - it is directly on top of the air bag and goes to the solenoid). On the cable, which goes back to the engine area, there is constantly about 12 V (hot at all times?!), but on the other hand there is for some reason no ground.

Each solenoid gets continuous 12-volts from the battery at the Black/Yellow stripe lead. So measuring 12-volts at one side of each connector is normal. The other lead, or grounding lead, runs back to the control unit. You will only see continuity (ground) between this lead and the car body when the ignition switch and air suspension system are on AND the control unit turns on the internal switch to open the solenoid.

5151 mm wrote: So we let the connector disconnected and took an external battery and put manually 12 V with + and - directly into the solenoid. Guess what, the solenoid finally opened! Cool! But you have to keep the external battery feeding the solenoid, otherwise the solenoid / vent (however you want to call it) will immediately close again. We just turned the ignition ON and let the compressor run and also let the one front solenoid open (feeded by the external battery). The compressor filled the rear and the one front corner all at once. But very slow. Very. The car raised, even the heavy front. We did the same with the other side's front solenoid. Finally the car is (manually) put in trim level. Nice! Finally some real ground clearance at all 4 corners!! Cool.

As you can see, the solenoid open and stay open only when 12-volt power is applied. Once the power is removed, the solenoid closes. Now that you got the car to trim height and turned off the air suspension switch, does the suspension stay aired up? If so, then the sealing of the solenoids is not an issue as I may have thought previously.

5151 mm wrote:The main question is: Why does the front solenoids never get opened by the system?
Where do I find a wiring diagram?

First of all, I provided the wiring diagram in my previous response. What worries me now is finding those wires to the front solenoids bare of insulation. If the two wires in the cable to each solenoid were somehow wrapped together as one, then the 12-volt power will bypass the solenoid and the solenoid will not open. I suggest testing the integrity of the grounding wires (Light Green/Orange stripe on the left side and Orange/Red stripe on the right side) between the two front solenoid connectors and the connector to the computer to make sure they are continuous and there is no 12-volt power present in these wires when the front solenoid connectors are disconnected from the solenoids. If either or both of these wires are broken, or they have been mistakenly spliced to the battery lead wires before the solenoids, the respective solenoid will not open automatically. If you need detailed instructions on how to do this, let me know.
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Re: functional principle of air suspension

Postby 5151 mm » Mon Mar 14, 2011 9:27 am

Thanks K-MANIAC!
What is supposed to happen, when I turn the suspension switch OFF?
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Re: functional principle of air suspension

Postby K MANIAC » Mon Mar 14, 2011 10:46 am

5151 mm wrote:What is supposed to happen, when I turn the suspension switch OFF?

When you turn off the air suspension switch, the "check suspension" light will illuminate, and the control unit will cease to provide automatic leveling. The compressor will remain off, the solenoids will remain closed and the vent valve will not open. As long as the solenoid valves seal air tight, the o-ring seals on the solenoids are air tight, and the springs bladders don't leak, the suspension will remain at it's current height indefinitely.

Back in December, during a course of rainy weather, I started to experience front end dropping issues with my Continental due to residual moisture in the system. Once I got a nice warm and dry day, I was able to pump up the system again, then turned off the air suspension switch. I have been driving the car this way for the last three months without any loss in air. But the air in the springs is sensitive to outside temperature. On cold mornings, the Continental sits visibly lower. In the afternoon when the outside temperature is higher, the car sits visibly higher. This is all due to the expansion and contraction of the air inside the springs due to temperture.

If you ever suspect a leak in one or more air springs, the best way to isolate this problem is to air up the suspension and turn it off and keep it off. The car will drop at the corner, or corners, where the air is leaking. This is a very handy trouble-shooting tip.
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Re: functional principle of air suspension

Postby 5151 mm » Mon Mar 14, 2011 10:47 am

Oh, I see you already mentioned this...
K MANIAC wrote:...
Now that you got the car to trim height and turned off the air suspension switch, does the suspension stay aired up? If so, then the sealing of the solenoids is not an issue as I may have thought previously.
...


My answer: No. I keep the switch ON. Because otherwise (switch OFF) the rear of the car drops very fast, like the solenoids would be completely open. The front never changes, like I mentioned and complained about previously. The front lets no air in, no air out.
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Re: functional principle of air suspension

Postby K MANIAC » Mon Mar 14, 2011 11:06 am

5151 mm wrote:Oh, I see you already mentioned this...
K MANIAC wrote:...
Now that you got the car to trim height and turned off the air suspension switch, does the suspension stay aired up? If so, then the sealing of the solenoids is not an issue as I may have thought previously.
...


My answer: No. I keep the switch ON. Because otherwise the rear of the car drops very fast, like the solenoids would be completely open. The front never changes, like I mentioned and complained about previously. The front lets no air in, no air out.


5151 mm wrote:So we let the connector disconnected and took an external battery and put manually 12 V with + and - directly into the solenoid. Guess what, the solenoid finally opened! Cool! We just turned the ignition ON and let the compressor run and also let the one front solenoid open (feeded by the external battery). The compressor filled the rear and the one front corner all at once. But very slow. Very. The car raised, even the heavy front. We did the same with the other side's front solenoid. Finally the car is (manually) put in trim level. Nice! Finally some real ground clearance at all 4 corners!! Cool.


My suggestion to you: Air up the suspension to trim level as you did before and described above, then turn OFF the air suspension switch and keep it OFF. If, in this arrangement, any corner of the car drops, then you have a LEAK, at any and all corners that drop. If this is the case, repair all the leaks first, before going any farther. If this means replacing all four of your solenoids, then, by all means, REPLACE THEM! They are 21 years old, after all.
"This car may be old, but it will still climb Kirker Pass at 110!"- quote of the original owner of my green 1964 Chrysler 300-K

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Re: functional principle of air suspension

Postby 5151 mm » Mon Mar 14, 2011 11:13 am

K MANIAC wrote:...
If, in this arrangement, any corner of the car drops, then you have a LEAK, at any and all corners that drop. If this is the case, repair all the leaks first, before going any farther.
...



Hmmmm

This is strange, dude :lol: :?

In this case, I would have to replace both rear solenoids. But I can't understand why I should do. The rear stays up with no problems. Indefinitely. At least as long as I don't hit the button OFF with my finger in the trunk. It seems like an electrical problem, instead of a mechanical. If I would have a leak in the rear, why is my car after several days (switch always ON) not touching the concret ground??
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Re: functional principle of air suspension

Postby K MANIAC » Mon Mar 14, 2011 11:41 am

5151 mm wrote:The rear stays up with no problems. Indefinitely. At least as long as I don't hit the button OFF with my finger in the trunk. It seems like an electrical problem, instead of a mechanical. If I would have a leak in the rear, why is my car after several days (switch always ON) not touching the concret ground??


Johannes, thank you. You have given me more information to work with.

If your car stays level with the ignition off and air suspension switch on, and the compressor does not run at all to maintain that level, I would suspect an issue with the control unit. Try this: Air up the suspension again. Once it is level, disconnect the battery. Then turn off the air suspension switch, in this order. If the car stays level this way, you don't have a leak. Next, reconnect the battery with the air suspension switch off. if the car drops immediately now, then your control box is the problem. Let me know what happens.
"This car may be old, but it will still climb Kirker Pass at 110!"- quote of the original owner of my green 1964 Chrysler 300-K

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Re: functional principle of air suspension

Postby 5151 mm » Mon Mar 14, 2011 12:13 pm

I tried that.

K MANIAC wrote:Try this: Air up the suspension again.

I don't have to, car is in level 8-)

K MANIAC wrote:Once it is level, disconnect the battery. Then turn off the air suspension switch, in this order.

Done that. Car stays level.

K MANIAC wrote:Next, reconnect the battery with the air suspension switch off.

Done that + ignition OFF: Car stays level.
Done that + ignition ON: Rear of car drops immediately.

;)
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Re: functional principle of air suspension

Postby K MANIAC » Mon Mar 14, 2011 12:26 pm

5151 mm wrote:I tried that.

K MANIAC wrote:Try this: Air up the suspension again.

I don't have to, car is in level 8-)

K MANIAC wrote:Once it is level, disconnect the battery. Then turn off the air suspension switch, in this order.

Done that. Car stays level.

K MANIAC wrote:Next, reconnect the battery with the air suspension switch off.

Done that + ignition OFF: Car stays level.
Done that + ignition ON: Rear of car drops immediately.

;)


I say you need a new control box. I suspect, as you did earlier, that the stripped and bare wires to the front solenoids may have shorted together, damaging the control unit. Before you install a replacement control unit, make sure you don't have any voltage leaking into the control box from the front solenoid signal wires when the front solenoid connectors are disconnected. If you need a control box, I have one out of a '92 Mark VII sitting on a shelf over here.
"This car may be old, but it will still climb Kirker Pass at 110!"- quote of the original owner of my green 1964 Chrysler 300-K

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Re: functional principle of air suspension

Postby 5151 mm » Mon Mar 14, 2011 12:34 pm

You finally understand the current condition of our Mark VII and my thoughts. Nice :D
Before I'll order a new suspension control unit I will check all the wires back there in the trunk around the suspension switch and suspension control unit. Since I now have a very nice diagram of the wires all I need now is a little bit more time to go through the whole system. A new control unit is f*cking expensive. Maybe I come back to you anyway... = thanks for your offer :mrgreen:
And thanks for all the time you spend thinking, writing and dialoging with me!!
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Re: functional principle of air suspension

Postby 5151 mm » Wed Mar 16, 2011 3:40 pm

K MANIAC wrote:Below is the wiring schematic for the air suspension system from the 1989 EVTM.[/size]Image
Image



Are FUSE LINK H and FUSE LINK L in the driver's feet area located? Very hard to reach something down there... Who designed this???

Do you have a diagram of the inside of the suspension electronic control module?
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Re: functional principle of air suspension

Postby CDW6212R » Wed Mar 16, 2011 3:50 pm

Those are likely at the starter solenoid, almost all of the fusible links are there.

Check those starter solenoid wires carefully and the way they are attached, organized. It is somewhat common for people to get those mixed up when they take them off of the solenoid for any reason. There are lots of pictures here of the solenoid and battery area, compare them to how your wires are routed.
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Re: functional principle of air suspension

Postby K MANIAC » Wed Mar 16, 2011 3:56 pm

5151 mm wrote:Are FUSE LINK H and FUSE LINK L in the driver's feet area located? Very hard to reach something down there... Who designed this???

Yes, they are. The diagrams below should help you locate them.

Image
Image
Image

5151 mm wrote:Do you have a diagram of the inside of the suspension electronic control module?

The operational schematics of the solid state components, such as the suspension control unit, were not provided in the service manuals. Ford technicians were directed to replace these "nonservicable" parts if they found them faulty in any way.

BTW - If you have 12-volt power at the power terminal of each solenoid connector (when disconnected) AND 12-volt power at the two pins of the compressor relay connector (when disconnected), then the two fuse links in questions are good. The power at these connectors is easier to check with a volt meter than trying to locate and test the fuse links directly.
"This car may be old, but it will still climb Kirker Pass at 110!"- quote of the original owner of my green 1964 Chrysler 300-K

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Re: functional principle of air suspension

Postby 5151 mm » Tue Mar 22, 2011 3:00 pm

I and two electric-gurus had time to work on the car again.
We removed the suspension control module, opened the whole unit and looked inside.

Image


Conclusion:
Two transistors are shot, dead, not working (however you call it) = the control modul is faulty! Port #12 (to the right front solenoid) and port #11 (to the left front solenoid) will never get any signal.
This means that my expectations were right :D The suspension really has an electrical issue!
Here we go...
So both gurus just build two additional switches, put them near the controle module, into the trunk. One switch for the right front solenoid. The other one for the left front solenoid. Those switches were wired into the system, in a way they can bypass the suspension control module. Now I can open each front solenoid manually. If I want to let them delfate: I can open the solenoids ayntime the compressor isn't running. If I want to inflate the front air bags: I can open the solenoids while compressor running.
Now this is just a temporary solution. The gurus try to find some new transistors to exchange them.

One more thing that's also not working is, that if I turn the suspension switch OFF, for some reason both rear solenoids get a signal to open and the air bags will deflate immediately.
BTW: Is there a "supposed-to-be way" a Mark VII owner can make the air bags deflate, if he wants to?
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