95 Roadmaster Automatic Level Control

[akreuz]

My 95 Roadmaster Estate’s Automatic Level Control (ALC) compressor runs excessively and there is little to no change in the level of the car. Does anyone have any details on the operation of this system? I was told that some of GM ALC systems there is also a pressure sensor that is used in the algorithm for level setting. On the surface, it seems either I have a leak or the compressor is shot. Any suggestions for troubleshooting anyone may have would be great.
Thanks

[gn1220]

If the compressor is running all of the time, as long as it sounds ok, I would say it is fine. When mine went bad it made some very nasty sounds. I would say your shocks are worn and leaking. Again, mine were bad and had oil all over them and would not raise the car a bit. Check the condition of the shocks and post your findings.

[barry eplorer]

I have a 96 roadmaster wagon, this may help... I have worked on my system and replaced the shocks and dump valve (factory origional parts) with the aid of my GM workshop manual.
System activates when ignition is turned on and remains active until 6 mins after switching ingnition off.
Auto level sensor is located just above the rear axle
Compressor and dump valve is mounted front, left, inside the bumper.
Compressor head houses the dump valve.
There is a 8-15 second delay in the sensor cicuit to prevent compressor/dump valve operation during normal driving.
Sensor also limits compressor run time/dump valve energisation to 6 mins incase of severe system leak - turning ignition on & off resets the run time.
An air replenishment cycle is initiated when the ignition is turned on - if the vehicle is a the correct hieght a timer starts and after 35 - 40 seconds the compressor will run for about 4 seconds the ensure that the shocks are filled with adequate residual pressure.(8-14 psi) If weight is added to the vehicle during the replenishment cycle then replenishment is overiden.
To reduce compressor starting current the dump valve is opened for 1.5 sec. each time the compressor starts.

The body trim (in line with the center of the rear wheel) should be 21.9" +or- 1"
After turning on the ignition and allowing the replenishment cycle to complete, add 300 pounds(1,2or3 friends depending on size) to the rear tailgate and observe the drop in ride hight. after 8-15 seconds you should hear the compressor start (listen closely by the front left fender and you will even hear the 1.5 second dump valve operation).then with the 300 pounds stil on the tailgate observe the body trim moving up towards the 21.9" mark. The compressor should cut off and your Wagon will stay at the correct hieght.
Remove the load (wagon will rise too hight) and listen again near the compressor-after 8-15 seconds you should hear the airescaping through the dump valve.

That is how it is supposed to work! Troubleshooting tips and covering all possibilities would take more time than I have to spare. But if you find that you need parts I found some (alot cheaper than dealer) at...

http://www.gmpartsdirect.com/partsvoice/frameset.cfm

you can also find the Original dealer workshop manual on line at Ebay motors for about $120 (or as I look at it a couple of hours in the dealership)