FAQ: Automatic Leveling Control (ALC) Concerns

gunmetalRED wrote:

Thank you so much you guys for all the information! I really do appreciate it.

Unfortunately in the last 20 minutes we discovered the crack in the rear cross member/subframe... so the ALC issue is now the least of my baby's issues. Just in the last weekend of driving, it separated. There is not enough metal left to have it welded. I am so freaking upset.

So if anyone in the Toledo, OH area is looking for a great parts car... EVERYTHING works... Brand new tires too... and I have one free tow left from AAA within a 100-mile radius. (sob)

Er, well. Everything works except somethin' with the ALC, of course.

The rear subframe can be removed and repaired.

Oddly enough, http://www.gmpartsclub.com/ shows them (subframes) on their inventory. I did not phone them... Maybe you should have a look at the site.

Albertj

I noticed that the rear end on my Riv is low to the ground.  The compressor runs when I manually move the arm up.  But if I leave it set where it has always been at, the rear end is to low to the ground.  I don't think it has moved since you can see the outline of where it has been set at.  Nothing looks bent or broken. Could it be the springs or something else with the compressor system?

If the air shocks are bad, the compressor will run for a while then time-out. Consult the service manual for length of run, timeout logic.
, and restart based on system inputs.

98riv wrote:

I noticed that the rear end on my Riv is low to the ground.  The compressor runs when I manually move the arm up.  But if I leave it set where it has always been at, the rear end is to low to the ground.  I don't think it has moved since you can see the outline of where it has been set at.  Nothing looks bent or broken. Could it be the springs or something else with the compressor system?

albertj wrote:

If the air shocks are bad, the compressor will run for a while then time-out.  Consult the service manual for length of run, timeout logic.
, and restart based on system inputs.  

98riv wrote:

I noticed that the rear end on my Riv is low to the ground.  The compressor runs when I manually move the arm up.  But if I leave it set where it has always been at, the rear end is to low to the ground.  I don't think it has moved since you can see the outline of where it has been set at.  Nothing looks bent or broken.  Could it be the springs or something else with the compressor system?

I don't think the air shocks are bad.  They seem to be holding air fine.  I ran through the service manual checklist and it narrowed it down to the box with the little arm that is connected to the control arm on the left side of the car.  It would work when I manually moved the switch higher.  I adjusted it so that it would keep the rear end higher, but I didn't think you usually had to adjust it once it has been set.  So I was wondering if something was worn out and was causing it sit lower than it should or if the switch is going bad and it is making the car think it is in the right position even though it is sitting low.

Is the bracket that the ALC sensor sits on all rusty? I know the one on my car has rusted pretty badly. Over time, and all these fine Michigan roads, the bracket seems to "sag" a bit. I find myself bending the bracket upwards every now and again to get the car level.

Unfortunately, there isn't a zero point on our cars for the ALC. The ride height specifically depends on the location of that sensor, rod, and control arm. The ride height wasn't adjustable until later on (early 2000's).

The only way to see what that sensor is doing is with a Tech II. You can access the RIM (Rear Integration Module) with it and read the sensor voltage. That's about it....

Abaddon wrote:

Is the bracket that the ALC sensor sits on all rusty? I know the one on my car has rusted pretty badly. Over time, and all these fine Michigan roads, the bracket seems to "sag" a bit. I find myself bending the bracket upwards every now and again to get the car level.

Unfortunately, there isn't a zero point on our cars for the ALC. The ride height specifically depends on the location of that sensor, rod, and control arm. The ride height wasn't adjustable until later on (early 2000's).

The only way to see what that sensor is doing is with a Tech II. You can access the RIM (Rear Integration Module) with it and read the sensor voltage. That's about it....

It is rusty, so it is possible that it has sagged some. I'll take another look at the bracket and see if it needs to be bent back up. Thanks for the help.

Today I noticed that the vacuum lines on the pump were falling apart in my hand.  Changed out the lines (7/16" diameter) and put some rust proof paint on the brackets.  Hoping it fixes the problem with loosing air if I don't use the car for a few days.  I also noticed that the filter material on the pump was completely gone.  It had been pulling in unfiltered air.  The intake does pull in air from the frame rail, so hopefully it kept most of the junk out of it.  So if others also have a problem with air leaking out, also check the vacuum lines on the pump.  Also wouldn't hurt to check to see if your filter was still intact.

Just a couple ideas for those interested in fixing your failed auto leveling set-up:

Idea #1 Replace your pump with an Air Lift 16060 12V pump, available at Summit Racing for $50.

http://www.summitracing.com/parts/air-16060/overview/

To use this pump, you'll need to adapt the fittings, which I'm sure can be done with a few parts from the hardware store. Also you need to mount and wire the pump to turn on/off with the OEM auto level switch. It would take some experimenting but should be doable.

The 16060 pump can create 100PSI and looks like it would be happiest mounted inside the car. I have no idea how loud it is, or its level of durability. If you want to step up to a better pump, here is a nice model 90C from Viair for $65:

http://www.sdsmarket.com/Viair_90C_12_Volt_Air_Compressor_Kit_p/viair_90.htm


Idea #2 This is a perfect complement to the manual fill air line kit. Rather than auto level or manually fill system, why not an auto pressuring system? I'm in the process of building such a system for my GTO, which will soon get rear air bags. The premise of the system is to control the pump using an adjustable pressure electric switch. One that seems well-suited is the Airtrol F-4200-100:

http://www.airtrolinc.com/components/f4200.htm

http://www.ebay.com/itm/AirTrol-F-4200-100-Pressure-Electric-Switch-/321210057381?pt=LH_DefaultDomain_0&hash=item4ac99c82a5

Basically it's a NO/NC relay that turns on the pump whenever pressure drops below a set value. There is an adjustment screw that lets you dial in a 1-100 PSI threshold. I think the pump wiring would connect to the "NC" terminal. That way when pressure is achieved, the switch opens, cutting power to the pump.

In order to lower the car, you will need a release valve or regulator to bleed air from the system.

In August of 2013, I posted in the "parts wanted" section a request for help in locating GM part #22153656, which is the level sensor for the Automatic Level Control (ALC) air suspension rear shocks on the 1997-1999 Rivieras.

Through the assistance of someone who was willing to find and pull one from a Buick Park Avenue in a recycling yard, and then ship it to me after payment for the part and his time, I was able to have this used part installed in my 1999 Riviera with less than 32,000 original miles on it. The problem I was experiencing was that the rear shocks were pumped-up too high, almost to their maximum limit, and not coming down back to level. The installation of the salvaged level sensor cured the problem...for just 3 months. Now the same behavior is happening again.

Obviously, the compressor works as it should and the air ride shocks are holding the pressurized air without leaking. Even if I rock the rear bumper up and down on a level surface, whether the engine is running or not, the rear end remains pumped-up and doesn't return to a normal attitude even after driving the car for 50+ miles at a time. The rear end is very stiff and unforgiving when going over bumps. One thing I did notice is that the only time I ever hear the compressor run is about 30 seconds after I start the engine, whether the car is in still in park or after I've shifted into drive - it seems I never hear it run to deflate the shocks or at any other time. I'm afraid to drive the car for fear of damaging the rear suspension components or having the lower front air deflector hit something.

I'm the second owner, the car was and is always garaged, seldom driven in snow and was in nearly new condition when I acquired it. I previously owned a 1997 Riviera, purchased new by me, for 16+ years and logged over 200,000 miles, and never experienced any problem with the Automatic Level Control system in the slightest. What do you think could be causing this reoccurrence of the same problem on my 1999? Could this be an electrical problem that is shorting-out the level sensor? Or perhaps a valve is stuck in the "closed" position and will not allow the release of air pressure in the system? Or something else?

I had a '92 Riviera, similar system, that had the same problem, went to full air when my level sensor went bad, and once I replaced it I didn't have the problem again? I also used one out of a salvage yard since the dealer wanted $343 for it, they were still available at the time, and I was able to get one from the salvage yard for $35. I don't know if wiring or any other assembly would cause the "same" problem, or cause the sensor to go bad, possibly you have just gotten a couple of weak/faulty sensors?
 
Sorry I can't be more helpful but it sounds like the sensor again to me.

It could be anything from a defective part to a simple broken wire. There is a very good diagnostic in the FSM. There are several charts in the FSM, you would follow the one entitled, "Back of car too high". You need a multi meter and time to follow the chart. It will isolate the problem so you can repair it. Anytime you cycle the ignition switch, there is a 17-35 second delay, and then the compressor runs for 3-5 seconds as a check. That is normal. I had a problem with the back of the car being too low, and I never heard the compressor after starting the car. I followed the diagnostic. It was a bad wire between the level sensor and the ALC relay under the rear seat. I never would have found it without the diagnostic chart. Sorry, but there is no shortcut here. You have to diagnose it with testing. Doing anything else just results in frustration and/or replacing unnecessary parts.

The compressor is supposed to run for a few seconds about 30 seconds to 1 minutes after startup, nothing to do with the actual position of the level sensor. It's part of a power-on system test. It should then exhaust back down to the previous level.

It sounds to me like the exhaust solenoid is frozen or not working right. Follow the FSM as Larry suggests.

I just replaced my blown rear air shocks (they were definitely original) with the Monroe direct fit shocks. Put them in, dropped the car, connected the air lines and put the relay back in for the ELC to kick the compressor on. What is the normal operation supposed to be like for this system on new shocks? The compressor does run, and I've checked all the lines and can't find any leaks...but the bottoms of my rear tires are still kicked out a bit (negative camber? I think). The rear end still looks a bit low, and my compressor seems to run for a bit after parking and definitely while driving. I just parked it after driving it about 5 miles, and the compressor did run for about a minute and then shut off. It hasn't come back on in the past 30 minutes, and I couldn't find any leaks. Do these cars require some kind of rear end adjustment? Or is my ride height sensor possibly toast? I found the unit, on the driver's side...it was connected to the rear suspension components with some kind of bar. Is any part of this sensor supposed to move? It seems to be stuck, if so. I just put new tires on the rear and don't want them chewed up because of bad alignment...

The sensor moves with the suspension, that's how it knows if it needs air, or to let some out based on ride height. You cannot physically move the sensor with it connected to the lower control arm.
My air compressor comes on for about 4-5 seconds every time I start the car (if it sat for more than a couple hours).

Just how low is it?

I can't find my tape measure for the life of me, but there's a shot of the driver's side rear. This was after the car sat for a few hours, and of course after the new shocks were put on. I think I may just be a little paranoid. It doesn't seem to run at all just sitting. Once I start the car, after about 5 seconds it runs for 30 seconds or so and then appears to shut off.

I guess my concern now would be the negative camber, but another post on another site said that slight negative camber was normal for these cars...so who knows.

The rear end on the Rivs does sit a little higher than the front. I'd say that as long as your car sits higher in the rear, or even parallel, everything is fine as far as the ALC system.

All of GM's cars have quite a bit of negative camber on them. However, it's usually no more than 1*. If you have excessive camber in the rear, and its really noticeable, I might be concerned about something being bent or worn out.

Can we get a pic from the rear? (car only please)

Lol I'll get a picture of the back of my car when I get off work. I'll try to get some pics of the suspension components as well. I don't think the rear sits higher than the front, there seems to be more gap between the top of the tire to the bottom of the wheel well trim in the front than in the back, if that makes any sense.

My shocks were completely blown, the bags had disintegrated and oil was all over the place. I'm not sure how long they have been like that due to previous owner neglect, so I'm wondering if my springs in the rear might be a little tired.

billfrank85 wrote:

My shocks were completely blown, the bags had disintegrated and oil was all over the place. I'm not sure how long they have been like that due to previous owner neglect, so I'm wondering if my springs in the rear might be a little tired.

I get it. There is a R.I.M. (Rear Integration Module) that controls the ALC components. It uses a 256 bit setup where 128 is the "center" of the ride height. Over time, the RIM will learn where your trim level is most of the time, and will change the trim setting on its own. The only way to recalibrate it is with a Tech II. I've had quite a few cars with the older ALC system in it that I've had to recalibrate after repairing. All I have to do really is raise or lower the car accordingly and relearn the trimset. Sometimes it takes a test drive or two to get it right, but it works.

Your car should still sit at normal trim height even if the springs are sagging. The shocks would still hold it up....it would just be a bit bouncy.

It does look low. Have you visually checked the lines on the pump itself? I was loosing air in mine because the stock rubber lines on the pump were cracked and flaking off. You can also adjust the sensor on the drivers side of the car by either bending the bracket up a little bit or on the arm of the sensor. If you look at the last page of this thread and the first posts of this thread you can see a discussion about the problem I had.

BTW it's totally normal for the system to self-test after you start the car. It should inflate/deflate the system and it usually happens within a minute of startup. After that self-test it generally won't run unless you put something in the trunk.

For a test you can sit on the back bumper for a minute and it should kick on, then get off and the car should rise up, and then lower. That tells you that the basics are working right. If it keeps turning on beyond that, there could be a small leak somewhere.

The camber issue isn't really related to the shocks. It shouldn't drop enough to affect that, even with a small leak.

If the rear of the car is low, it will have more negative camber than it should. When I first bought my Riviera, the ALC was not working at all, and I was unaware of it. One day, a friend following me in another car commented that it appeared that my tires looked tilted in at the top. Thinking it was an alignment issue, I took it in to a friend's shop. When we discovered there was no camber adjustment at the rear, my friend commented that the back of the car was low. While it was on the alignment rack, we physically lifted up on the rear of the car, and you could see the camber change in a positive direction. I subsequently went through the diagnostic in the FSM for "Back of Car too low", and eventually discovered a broken wire between the level sensor and the rear fuse/relay block under the rear seat. Every time you start the car, or cycle the ignition switch, the system will self test after a 17-35 second delay. The compressor will run from 3-5 seconds.

Great info Larry! Okay, so get the height set properly first.

When I turn the key, or start the car, the compressor kicks on after a few seconds and runs for maybe a minute or two. If I park it and shut it off, it runs for another minute or two...maybe even a little more. It never runs just parked. From what it sounds like, that seems like normal operation but is it normal for it to run that long at those times?

As far as "setting the ride height" are you referring to the process that requires a scanner? Sounds like an expensive dealership only fix...ugh.

.