Well, gonna try this out because everyone i've talked to and every techline i have called has had no help to offer.
The vehicle: '04 H2 with air suspension

The problem: Right rear air spring drops randomly.Might go a week without acting up might only go a couple days or hours.

What's been done: Vehicle came in originally for whole rear dropping and compressor not functioning. Replaced compressor assembly with new twin setup, set trim height. Worked fine for a week or so then right rear started dropping randomly. Left side air bag will have pressure, right will be almost empty. No codes set, no service air ride message. Ride height sensors reading properly. The sensors would see the difference in height, but the computer did not turn on compressor or try to compensate for it. Defected the compressor assembly and got a new one. 3 days later, same problem, right rear drops. If i hit the extended ride height button the truck will raise up as it should, both sides at same height. I hit the button to lower it back down and it drops and sits level on both sides....until it acts up again in a few days. Replaced right ride height sensor on a whim, no change. No leaks in bags, lines or fittings. I have checked for high resistance in all the sensor wires from the sensor connectors all the way to the connector on the control module- nothing, all good. I have called the hummer dealer in cincinnati numerous times, and they have been very polite and attempted to help, but they are as stumped as i am. The only code the system has ever shown is a history code of C0711- Air suspension pressure sensor. This sensor is part of the compressor assembly.... i know i didn't get two bad ones from hummer so i think this code is setting when the problem occurs due to the drop in the one side i don't believe it is related to the right rear dropping.
I am lost and out of idea's I'm not a hummer specialist, but we do work on a small number of them at our shop and i'm pretty familar with the air system on these things and this one is throwing me for a loop. The other strang thing is that just to try to rule out a bad spot in a height sensor, i disconnected the sensors and tied them in the normal hieght range.... right rear did not drop in 2 weeks..... that's why i replaced the sensor, but it still does the same damn thing HELP!!! anyone, any input is welcome i'm ready to light this one on fire and claim it on insurance just to get rid of it!

 

I would try putting a shut off in the right air line , pump the compresser to the normal ride height , then shut off the right side to see if you will loose air on the right side , i would say you might have a computer problem or modual problem , if you are getting the input from the sensor to raise or turn on the comprsser and its not , that might be a bad output ,,
i would try a couple differnt things ,, what happens if the truck is at ride height and the left side air is bleed off at a line will the compresser turn on to fix the problem ? is it both sides , thats it not controlling or just the right ,, you could have 2 problems one the dump valve for the right side might let air out over time and the compresser is not turning on ,
but what if you tie both sides into one line ,just the right side ,,
just some things to try to narrow the problem down..good luck mike

 

well, i'm seriously doubting i have a leak anywhere. The truck sat in the shop over the weekend and didnt drop at all. It's only the right side that drops. Right air bag will be near empty when this happens and left will be full. I also have a hard time thinking it's a module issue because this is the second compressor/module assembly that has been put on and has the same problem. If i bleed air out the compressor will kick on and adjust accordingly. Although, another strang thing is that the right side always sits about half to 3/4 inch lower than the left even after proper trim height calibration. The sensors show the difference there too, but it never tries to level out. The sensors stay within .25 volts of each other and i've seen numerous other trucks that sit the same so i didn't think to much of it. I've got a left side height sensor ordered simply because im plain out of idea's i'll post on what happens with that, but i'm not feeling optimistic about it.

 

i know you have a sensor ordered , but how hard would it be to swap sensors and redo the air bleed offf and then pump the lines back up ?would be interesting to see if the problem switchs sides .
mike

 

trash in valve letting air bleed off

 

Easier solution would be to ditch it all together. nothing but trouble. I removed mine for a set of springs. Was just as comfy with no issues to worry about.

 

Don,

It is the AirSpring. I know these systems inside and out. Trust me on this. I am a Cincinnati guy. If you need some help let me know.... just end me an email I will give you a call to better explain.

 

eric, sorry haven't had a chance to check this page since two days ago. The vehicle has new air springs on it, replaced less than a year ago and i've been over these things with soapy water and a magnifying glass a few times. Can they bleed off intermittently? There is no valving on the spring itself so unless there is a leak in the air bag itself how can it it bleed off? and if it was leaking, why not all the time? I did put the sensor on it the other day and it's been fine so far, but sometimes it takes a few days to act up. Some one said switch the sensors side to side....can't do that they are different on right and left, we were gonna try that a month ago and realized it wouldn't work. I gave the customer the option of going to coil springs but they wanted to keep the air ride and were willing to buy the new compressor. As i said, this is the second new, twin compressor assembly we have installed with the same results, it has never left the shop so i don't think there is any depris in the valve, i have looked for anyt sign of packing foam in any of the valves, but there come sealed and i can't see anything in them so i think that is ruled out..... I'm going to return the truck to the customer for the weekend and see if it acts up. i'll post back next week and let you all know what happens.

 

thanks for keeping us up todate ..good luck .mike

 

I'm with HumminNBoatin on this one.

When my bags went bad they would drop intermittently. I replaced one and was fine for a few months, then i started getting the problem again. I took it to my mechanic, and he sprayed it down and said he couldn't find a leak (nor could i), so i kept driving it for a while. It would drop again every once in a while. One day when i knew it was droping i went out and sprayed it and finally found the leak on the bag. It was not in a hard to see place or anything, so it wasn't like we just missed it. I guess sometimes when and where you park may seal the leak off. Everything has been fine since then and i am still on the old style compressor.

My guess is a bag was either damaged when it was put in or was faulty from the factory. I guess you could swap the two bags and see if it then drops the other side instead. Or better yet just replace the bag. I bet you wouldn't have any problems after that.

I've talked to other h2 owners who've had the intermittent drop, and so far, every one of them have fixed it by replacing the air bags.

Good luck on it.