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Drawings Provided By
Al Chernoff
  EL-II Level sensors and where to get them

There is some info on my site at

Some of the sensors are well hidden but any car with a compressor and air shocks should have one.  They can be under either side of the car, the clue to their position is the little rod attached to the rear suspension, you can seldom see the actual sensor without looking carefully. Dave

Gene--79 thru 85 Rivieras, Toros, Eldos, and 80 thru 85 Sevilles are the same, as are Cadillac Devilles. The easiest ones to get out are the 90 and later Devilles--be sure to check for the round connectors--at some point GM went to the rectangular connector which works but needs some rewiring. bobD

A great rundown by J Sharp


EL 1 has one compressor, mechanical ride height valves and an air tank.
EL 2 has photo-optic ride height sensors and two smaller compressors and no air tank.


As you know, the Electro Level I (as well as the Power Level), use a mechanical lever to add or exhaust air from the air bags while operating in the Automatic mode.  There is a time delay of several seconds in the in/out system per design.  Moving the linkage arm up or down should provide an action within a few seconds.  If not, then I would suspect a problem within the internal Height Control Valve system.  Since you have only identified a problem with the exhaust system, I would suspect that
the schraider (sp) valve (within the height control valve is stuck/plugged).  I think this section of the HCV can be removed/cleaned &/or replaced w/o major disassembly.  After repair, I would ecommend
that you "Back Flush" the system to remove any debris that may be trapped.  Air the system to normal height, place system into Hold, let the air out of the tank & remove the tank drain plug.  Place blocks under the boggies so that the coach can sit down an inch or so.  Now turn on the system & place both sides into the "Raise Mode".  Since the tank is empty, the air in the bags will exhaust back thru the tank & push any debris out of the lines/filters thru the open tank.  This works like a champ so that the air passage will be clean & open.  Turn off system, replace the tank plug & HAPPY LEVELING.


Trouble Shooting Tip for an air suspension leak down problem that occurs on one side only.
For test purpose, remove the lines going to the air bags at the 3rd solenoid (Hold solenoids,  blue & gray tubing) & replace them crossed to the solenoids.  Now air up the system & note height of each side.  Return later after the air leak down occurs. If the same air bag leaks down after the crossing of the air tubing, it means that the leak is occurring in the air bag tubing or the air bag itself.  If the leak crosses to the other side, it means that the air distribution system is leaking.  This procedure will quickly allow determination of the fault as being out side the coach or inside the coach (Air Distribution Area).
DIVIDE & CONQUER is the action that succeeds !!!!!!Duane Simmons

El Troubleshooting By
Mark Grady

EL troubleshooting class 301, with the sub-title "what the &^$% is wrong with my 3 way valves?"
Before we start, heed this advice from Prof Arch, who writes with wisdom:
>Check the little arms that go between the bogie and the ride level
>controller. The rubber on each end of mine was shot.

 Here's a simple test:
Put both sides in the raise position. Wait on the coach to go up. Center switch in 'auto', left and right in the center. Get out, walk up by the rear wheels. In 10-30 seconds, you should hear the hiss of air being let out of the bags. It isn't real loud. Your valves must be able to 'break wind' or they are mis-adjusted or bad. You must first solve this problem if it exists.

1). Adjust or replace the ride height valves.
2). Live with it. Use this procedure:
    A). Set level to 'auto', let the coach level, compressor turn off.
    B). Set level to 'hold', occasionally to 'auto' about once an hour while driving if you feel
          your   butt's dragging.(The coach, not yours).
3). Fix or replace the bad 3 way valves.

EL I height creep can be caused by leaking 3 way valves. We're talking about the three way valves that are mounted on the common air pressure manifold. This is easier to understand if you go to http://www.california.com/~eagle/figs/off.gif and print that schematic. Thanks to Al Chernoff and Eugene Fisher for a job well done. (see the top of this page)

Be aware now, before you start, this is going to get involved. You might want to take a Polaroid of the whole thing so you don't get lost.

I don't remember which side you said was creeping up. If I've picked the wrong side in this example, refer to this drawing for the correct colors. I'll detail this using the passenger (right) side of the coach.

Here's the technique:

1). Safely block the rear suspension of the coach prior to using the rocker switches to fully deflate the bags. I'd suggest a jack on the troubled side to make this easier.

2). Make sure you've got all the air out. Take the blue line from the air bag off the two way valve. Take the two way valve itself off the three way valve, or (if you can) take the second three way valve off the first three way valve. What ever works for your coach, leave the first three way valve connected to the pressure manifold. For the moment, leave the yellow air line attached to the valve.

3). You now have an open port on the three way valve. It's showtime.

4). Take off the wires that feed the driver's side two way valve. (Light green with a double black stripe). The driver's side two way valve is the one with the grey air line. We're going to take the driver's side air bag out of the circuit for a moment while we run some tests.

5). Depending on the pressure that's left in your air tank, it will vent when you take this next step, so be aware.

6). Turn on the ignition key and set the center EL I rocker to Auto. Air will start to come out of the open valve port. This assumes that the coach is below normal ride height, and the ride height control valve is calling for more air to be put in the bag. (If you jacked up the coach *above* the correct ride height before you started, this won't not happen.) For the moment, we'll assume that the coach is below the correct height, and that air is flowing out of the open three way valve. If you're following along on the printed schematic, this air is coming from the yellow line.

7). Turn off the key. Go outside the coach and disconnect the connecting link that goes from the boogies to the height valve. Move the height arm in the direction that would turn it off (against the internal resistance). Or, safely raise the coach up with a jack.

8). Turn on the key. Depending on how reactive your ride height valve is, air will stop coming out of the open three way valve port. If it doesn't, your ride height valve is shot. (We'll confirm that in a moment, but for now, we'll assume that the air flow has stopped, and the compressor may even shut off.) Get your soapy water spray, and soap up the open valve port.

9). Are there bubbles? This comes from only two places: the ride height valve is leaking through, or the three way valve is leaking through. If there aren't any bubbles, then you need to check how well the 3 way valve seals by cycling it.

10). Go to the EL I right rocker switch and push it to raise. Air will come blasting out of the valve opening. Flip it back to center, then to raise a couple of times. Back to the center and check for air leaking through the valve again.  If you now have bubbles, its the three way valve that's bad. If you always had bubbles, then we'll isolate where the problem is.

11). With the activator link on the ride height valve set as if the coach was at height or the coach jacked up, turn the ignition key on, move the right switch to raise and let off the air pressure. Turn off the key.

12). Take the yellow line off the 3 way valve. Center switch in Auto, right switch in the center position. Turn on the key and get some air pressure building. Is air escaping from the yellow line? Make sure the coach is above ride height, there should be no air flow. If there's air coming out of the yellow line, then the height valve is bad. Replace it.

11). If there is no air flow from the yellow line, check the open ports of the three way valve for leaks. If there is any air leaking through, you've found your culprit. There should be no airflow through the valve when it is off. Replace the three way valve, and reassemble everything.

(Note that it only took me three words to cover about 2 hours worth of work there at the end.)Remember to always work safely.



pictures of the switch internals
When I park my GMC at home and don't plan on using it for a few days, I put down my two rear electric stabilizer jacks and let the air out of my air bags.  Lately I have been having problems letting the air out of the let air bags so I thought I would take the dash electric control switch apart to see if that was the problem.

I had heard on the GMC net or somewhere that sometime it helps to blow the switch out with air to remove the dust that has collected over the years. In my case that didn't help any so I took the switch apart to look at the contact points.  These electric switches are made so they are very easy to disassemble.  All you need to take them apart is a small sharp pointed knife blade or screw driver.  There are four little spring loaded tabs that hold the switch together and all you need to do is bend them back a little and the back comes off the switches.

 I found my problem was corroded contact points where carbon had built up over the last 33 years.  I cleaned the switch insides and took a small Dermal rotary brush and cleaned the contact points, relubed the switch and put it back together with a new piece of foam rubber to seal it an it's probably good for another 33 years.

This all may have been discussed many times on the net but I couldn't find it on Gene Fishers site so I assumed it didn't exist.  Hopes this helps someone correct their problems down the line. Chuck Aulgur

Remove the L shaped spring clip retainer (#13) that holds the lever to the control arm of the valve. This clip is also a retainer for a rubber plug that is held in by the spring retainer clip. Remove the rubber plug and then you can look at the shaft and see if it moves when you work the lever. Hold
the lever to either position long enough for the shaft will be slow to move, as the valve has a delay system built into it. After approx. 10 or 20 seconds the shaft should slowly move, but not very far. For a better look you can also remove the four screws that hold the L shaped mounting bracket
to the valve and witness the movement of the Y shaped yoke. The yoke operates the two schrader valves that control the inflating or deflating of the air bag. Do not remove the retaining spring or the plug on the round cylinder part of the valve as this houses the fluid that gives the valve the delaying action. There are three fine mesh screens that are held in by the screw-in adapters for the air lines and the exhaust nipple. These screens will become clogged from a contaminated air system and will cause a lot of problems with the air bag system. You can remove the adapters and clean the screens with carb cleaner and reinstall them along with new "O" rings. These are the adapters that screw directly into the valve body, and the nylon air line adapter screw into these. Bob Drewes  
A GMC GreatLaker now has the capability to rebuild the height control valves back to new and they look new too.  His name is Dave Lenzi and he can be reached by E-mail at mlenzi@tir.com or 810-653-3902.

 How about a direct replacement leveling valve from these people.

Looks like they bought the rights to the valve from GM and may even have the brass fittings to replace the plastic ones.

It appears that the NEWAY #90054007 is the most common truck/trailer leveling valve.  Has delay, stated variously as 6-12 seconds.  It may be a final option for us if Dave Lenzi can't keep up with demand for rebuilt  steve

Power One
System description and testing/rebuild by Rob Allen
Picture of the airpump shut-off switch

If you can not find one locally, McMaster Carr has them www.Mcmaster.com   Page# 585
I recommend P# 4154K626   $32.90
P# 4154K616  for $29.38  will also work.  It just does not have the unloader valve. KenB

Power One from the top down

> Where do you get the air hoses and fittings?

The hose used is 1/4" DOT Nylon 11 tubing, which is available from truck supply stores and also from McMaster-Carr. The part number is 5097T41, and it is on Page 109 of the online McMaster-Carr catalog (www.mcmaster.com). It comes in a variety of colors and costs 34 cents a foot. The fittings are also available, part number 51835K1, and you supply the shape and select 1/4" tubing. These are compression fittings, usually made by Parker.  Denney

It takes three complete runs of hose from the control valves to each corner--one for the bag and two for the leveling valve.

The single tube from the right control valve to the right bag that goes from the valve, through the firewall down to the left frame rail, and then along the left frame rail to the rear suspension crossmember. Then, it goes across the coach, up through a routed-out opening in the floor above the right frame rail, and to the bag. I think I probably used about 30 feet, and a 26' coach would need two more. Plus or minus five feet.

I don't remember the official colors, and I have used black when I needed to replace something. But so far I have not replaced the leveling valve hoses to the back, and those are the ones that need color. All of it is currently 41 cents a foot at McMaster. They come in 25, 50, and 100-foot rolls (and longer). I would think that you'd need a 100-foot roll of black, and a 50-foot roll of the colors to the right rear. You *might* be able to get away with a 25-foot roll for the left rear, but I wouldn't risk it.

Or, you could buy a 250-foot roll of black and get the price break (33 cents a foot), and then label the lines or use colored tape to keep track of them.

The nylon tubing is pretty durable. I've only had to replace the sections that were physically damaged or that had be badly repaired. Replacing the line to the right bag remove three or four inline connectors that had not reason to be there.

The push-to-connect fittings work just fine, but the end of the hose must be cut clean and square with a razor blade, and then once you insert the hose, tug on it to make sure that the barb mechanism in the fitting has taken a bite. This also makes sure the release ring is fully in the unreleased position. I have had no leaks with mine where I've used them.

Of course, with a Slaten valve on one end, new tubing, and a Parker compression fitting on the other end, my right bag should hold indefinitely when the leveling valves are in Hold. But it doesn't--I think the bag fitting leaks. This is the threaded fitting that screws into the bag on the fill end, and it comes mounted on the bag. But if the big nut binds when being removed, it will unscrew this fitting. There is an O-ring down it it, but the tightening of the fitting is apparently critical. Next time I have the bag out, I'm epoxying that fitting into the bag. I can't think of why it ever needs to be removed. Denny

Support information
Your '75 Eleganza probably has the earlier Power Level system with the control valves on the dash, right? I'll assume so, and if it's a later Electro Level system someone else will answer your questions.

With the valves set to Hold, each valve is connected to the corresponding bag by a single, unbroken run of hose. Thus, if the coach loses air in Hold, it is either the bag, the control valves, or the hose between them.
Often, the hoses have been damaged and repaired using inline couplings. These may be hiding from you. Also, the fitting that comes  in the bag may have been turned during some prior installation or maintenance, damaging the O-ring inside the bag. If that's the case, you must remove the bag and replace the O-ring, and then I would seal the threads with Loctite (or something stronger--next time I'm using epoxy!). The fitting never needs to be removed from the bag except to make this repair. The hose connects to a fitting in the end of this fitting.

But usually it is the control valve that is leaking when in Hold mode. These will leak internally, allowing the bag pressure to bleed back into the tank. Usually, the tank side of the valves leaks because there are many connections and devices on that side and getting rid of all those leaks can be a challenge. Soap bubbles may not find a leak that only becomes apparent over several days.

You can rebuild the valves, but most find it easier and more effective to replace them with the much better valves made by J. R. Slaten. They are not that cheap but they make your valve problems go away immediately. And they work much better than the originals, even when the originals don't leak.

Getting to the point where Hold really holds is a good place to be. That will let you use the coach mostly as intended until you can go through the rest of system to make it work the way it should in Travel mode.

> Don't mind replacing the compressor.  What is the best fit and price?

  Seems > there are a couple of them out there.
The currently favored replacement pump is the Viair which comes in several sizes and duty cycles. All the appropriate choices are available from Scott Nehoda at Adohen Supply. I have the Viair 350C, which is a 100% duty-cycle replacement for the Dana pump.

Leveling Valve Repair / Rebuild /Replace (Power One)
Go in the driver's side of the engine compartment and disconnect all lines going into the coach. There are unions on all lines there.  This will allow you to pull the valves far enough from the instrument panel to get to the connectors on the back.

When you disassemble the valves, LOOSEN the three allen head bolts about 1/16th" and tap the side smartly with a screwdriver handle.  This should separate the halves without tearing the seal.  Very carefully loosen the seal from the front side of the valve. With luck you can reuse it. Once this is done, finish separation and remove the springs

Remove the O ring on the spring side of the valve.  You can then push the valve out thru the front. If it hangs up, that's pitting and corrosion in the cylinder. Work it back & forth with some penetrating oil and push it on out.

Then it's grind valve seat, hone cylinder, polish piston, clean up and reassemble. Incidentally, my coach is still standing tall - like someone slipped it a triple dose of VIAGRA.

Also removed the hose - compressor to check valve - at the check valve to see if I could detect a leak back thru the valve. I could not, so reattached the hose. The tank pressure is now holding. Go guess----------.  The check valve appears to be relatively new and is all brass.

Maybe you'll luck out, as I apparently have, and the leveling valves will solve your problem entirely.
Best regards,Waldo
Look under the back end of an old Caddy with an automatic leveling
set-up.  The arm and bracket will be different, but the basic valve
is the same piece. HTH
Gary Kosier
I found best cure for leaking level valves.  I replaced them with new up grade valve assembly built by JR Slaten in Louisville, KY. Since replacing old valves, I go months without leak-down. Been using new valves about five years and am totally satisified. Give him a call if yours still leak. His number is:
e-mail at: jrslaten@aol.com. Good luck.    Harry

rotary air valve piston seals
I got this info at a Classic rally and did mine. They are like new. Use Viton “O” rings - 007 on top of shaft and 008 on pistons. 90 deurometer hardness. Got them on the net. You have to clean up the bore, seats, and I polished the gasket faces with 800 paper on a glass plate. Al & Carol Scott

I assume you are asking about the O rings in the dash mounted control valves. These are #7 O rings that should be available at industrial suppliers or hardware stores. Use a little silicone grease when assembling. Denny

One of my first "projects" on the "Noble Beast" after we bought it in '99 was fixing a few leaks in the ElectroLevel system. One of the 3-way valves had a cracked housing and I ordered a replacement from Gateway. I just found the box it came in (I'm a packrat, what can I say!), so here's the part #:

Honeywell Skinner Valve
C 4 DK 1 150DC11AD

Honeywell Inc.
Skinner Valve
95 Edgewood Avenue
New Britain, CT 06051
(203) 827-2300