air shock compressor operation

So, I'm attacking my air shocks this weekend. When I got the wagon, the level sensor was disconnected accidentally or on purpose? I've tested the level sensors operation and the compressor starts running if I move the sensor to car low. this is good.

What it does not do is run when the key is turned to run. I was under the impression that even if at height, the compressor should run for a few seconds, after a few seconds of key run. To be honest, I had no idea I had air suspension.
What controls this operation? Is it based in the compressor, or the switch?

For now (like I was planning without knowing I had the air option) I'm just going to use the manual fill valve, but if I can make the auto function work, and the parts and wires are already there, it seems logical do get it working if reasonable.

The wagon pulls my popup and related items for our trips. I did consider bags, but I needed all 4 shocks anyways and monroe has a rebate deal that made the air shocks make plenty of sense. ($58 for all 4 shipped from rock after rebate)

The pump probably should not run if the sensor tells it that the car is above the trigger height. When the car is loaded, and the suspension is compressed the compressor will raise the car until it reaches the "minimum" height that the sensor determines. You can adjust the sensor rod length if you want it higher, or lower. Mine only ran at startup when the bags on the shocks leaked.

I installed a compressor and air lift bags on my 1st wagon, a 94 caprice. If I remember correctly, the level controller has some electronics in it to do a 'self check' upon startup. It would bleed down, then pump back up to height. There are no electronics at the compressor, save for the relay, which is clearly working. If it works but doesn't self test, I would leave it be. If you mean it wont run no matter where the sensor is, there could be a bad fuse or wire somewhere, as I am fairly sure there is a 'hot at all times' wire and a switched wire running to the controller. I can dig up some diagrams if needed

thanks for the info. I'm armed with a wiring diagram, but it does not show any of the internals of the level sensor, which I should call a controller now. There must be a problem in there. I'll be starting the work tonight and will have more info soon. I expect to find problems somewhere, the line to the compressor along the frame seems to have an excessive amount of tension on it as well. The shocks have no air in them, the bags are rotted and leak fluid. Funny enough they didn't seem all that bouncy. The good news is my wagon is not so rusty for a michigan ride, so maybe the blood will not escape on this repair, and I enjoy unusual electrical repairs. good shock replacing bad shocks is an instant gratification kinda thing too.

turnofftheradio wrote:

What it does not do is run when the key is turned to run.  I was under the impression that even if at height, the compressor should run for a few seconds, after a few seconds of key run.  To be honest, I had no idea I had air suspension.  
What controls this operation?  Is it based in the compressor, or the switch?

You are correct. It is called the air replenishment cycle.

Thanks haze thats helpful.

One off...

According to that page, if my sensor was sensing the need to lower at startup the compressor never does the run cycle. Since mine was off and at high sense it never ran. I finished the job, connected to the factory level and all is good! I was expecting way more problems. Cheers.

turnofftheradio wrote:

...I finished the job, connected to the factory level and all is good!  I was expecting  way more problems...

It's not often things turn out that way. It's a great feeling.

Seriously, i sent my wife and kids away thinking I would need nearly the whole day to fight those upper shock bolts. Way easier than I had expected. I used an offset box 13mm, and a 10mm on a long extension like most people suggest, but I added a strip of electrical tape between but and wrench so the nut but wouldn't fall out of the wrench. Thanks for the help guys!

well, short lived.  My compressor did not like being woken up.
It was leaking after some use.

It's ugly, the intake/vent hoses disintegrated. Possibly, a chunk of hose, or flake of paint, or rust something managed to get stuck on the pump valve and would not let it seal.  there are 2 valves, intake, closest to the solenoid, and exhaust with the visible spring.  they are plastic/rubber and spring loaded.  the seat of that exhaust valve was corroded and the chunk of debris landed on that valve.  the solenoid is the orange and white wires in the head.  so rusty.  there are 2 filters that should not let rusty solenoid to head but they are old.


this pic i'm holding the exhaust valve.  intake doesn't come out


I'm going to service this thing, but I don't really have any hope for it.  Junkyard adventure time.

for now I just used another tee and blocked off the compressor side, and use a manual fill, which doesn't leak.

If your cylinder and piston are good, you could transplant a donor head with the valves to yours.

With the piston about half-way up the cylinder, pour something benign like mineral spirits into the bore. If the solvent runs out quickly, the piston ring is bum. This is usually the case on a used one as well.

well, my piston seems to check ok. I'm getting good pressure, but it leaks down fast. I cant really tell if its the intake/exhaust valves or the release solenoid, but the air leaks out the intake tube so it's a head problem with one or more of those items involved. The smart thing to do would be to find a good entire replacement compressor assembly.

I added a fill port on outlet to see pressure, run pump to 90psi, put intake hose in water jar, observe many bubbles. fail pump.


I'm sure I can make a prettier bracket, but this thing was just laying in the part pile, and worked for now for the fill port.

There's a bunch of GM cars with on board compressors but you need a specific one. B/D body cars of course, but I found that chevy Venture vans (97-05 I believe) and it's brethren (Silhouette, Transport, Montana) use the same compressor, and are much easier to find and pull. They're  located under the floor behind the driver side rear wheel. Btw, the electrical circuit is the same as the under hood light, so if that light illuminates then the fuse is fine for the compressor.  I devised a test in the junkyard to test how well they run, which was powering the compressor with a cordless drill battery and hooking the outlet tube to a balloon. Faster it pumped up the better the pump. I may still have a good spare pump I could let go btw.

Here's a link to my air shocks and compressor saga. https://gmlongroof.4umer.com/t11577-finding-leaks-in-g67-air-suspension