Hi All,

I'm having the dreaded air suspension issues. Since obtaining the Hummer, I have replaced the air bags to resolve some of the leak issues. After still continuing to experience an on-off-on-off running compressor, I went spraying soap around, I found my leaks were coming from the inlet valves, not just inlet collars but also cracks around the body. I attempted cleaning it along with the o-rings inside, but there was no change. I tried filling the inlets and body cracks with epoxy as a last ditch effort to try to stop the leaks, but no dice. I have replaced the factory inlet valve assembly with aftermarket valves, set up like this video:
After doing this, I can't get the extended ride height to function correctly. When I press the button on the dash, it flashes orange like it normally would...but the light never goes solid. The only way to turn off the flashing light is to turn off the vehicle and start it back up. With the aftermarket inlet valves I put in from the above video, I can't find any leaks but something still is not right. The main visible issue is the continuously flashing extended ride height issue.

I am parked on a very slight slant, side to side not front to back. I haven't checked the values on a perfectly level surface yet, but I have some Tech2 readings I will post below. I'm hoping if someone here has a Tech2, they can provide me their values for comparison. I have a Tech2, I'm just not sure what the proper values are/should be. I'm not getting any error codes from the air suspension system. At normal ride height, outside measurements from ground to fender is 41.25" on the driver's side and 43.25" on the passenger side, a 2" variation in the height from one side to the other. While I'm parked on a slight slant, it's not a 2" variation.

At normal ride height, readings from Tech2:

Right height sensor: 2.71-2.73V
Left height sensor: 2.27V
Height sensor current: 19mA
Rear leveling air pressure voltage: .43-.45
Trim Height Learned: No
Left isolation valve: Inactive
Right isolation valve: Inactive

At first glance, I would think one of my ride height sensors is failing due to the differences in the voltage reading. Though, I'm not sure if my small slope is the cause of that or if those values are close enough together. I have tried searching many places for this, and every post involving a bad ride height sensor seems to cause an error code. But I don't have any error codes. Also, is "No" the correct value on the "Trim Height Learned" reading? Or does this sound like I need to re-calibrate the height of the rear?

I know I can switch over to coils and ditch the air, but I'm trying to do everything possible before going that route.

 

I would think that the sensor voltages will vary a bit more if not sitting on perfectly level ground. They will not be exact though.

I had a couple of settings from mine noted (this was on flat concrete).
Right - 2.59
Left - 2.41
Sensor current - 19ma

I did not have the other values noted...

I think you might need to do a trim height calibration though. You are supposed to use some special blocks that sit on the axle to do that. You can do it without those. You just need to block and support the rear when you do it. I used two jacks and jacked both sides to the exact same height when I did the calibration. Mine did also used to have a small amount of lean to one side which was fixed when I recalibrated it.

My setup was a bit different though - mine has the older single compressor style.

Here is some notes I made when I recalibrated mine....

You need to support the rear by the frame in the exact position you want it to be. This will become the new sensor reference point. Support the rear frame in this exact position with jack stands, jacks, blocks or whatever. Then with the Tech2 connected turn the truck on, get into the air ride menu and deflate the air ride so the truck is sitting on the supports you have under the frame. You do not need to let if fully deflate this time. It is not going to sag down due to the supports but let it air down a good bit. Shut the key off exit the menu, turn the key back on go back into the air ride menu and choose calibrate. Exit back out, shut everything off jack up and remove the supports under the frame, lower it down and cut the truck back on and the air compressor will start to reinflate to the new calibrated positions. Watch carefully to be sure that it stops at the right new height.
So – it is doable but it is fiddly and a bit of a pain.

I did have some notes from the GM service system as well. The sensor voltages should be between 2.06 and 2.88 volts when sitting on level ground so yours are in the correct range.

 

his setup with check valves coming right off the bags will not release pressure. it has a one way flow into the bags. you need to see where the factory unit has the bleed solenoid and try recreate that instead. most likely needs 3 to 4 solenoids to complete.

 

Well, crap. That makes sense. I wasn't really thinking this through when I was following the video.

 

you might be able to find what you need in this cataloug https://dscsystems.nl/media/download...209-9-2020.pdf
it is a possibility they are the OEM manufacturer of the unit.

 

ThePtero out of curiosity did you have any pictures of you old inlet valve assembly?

 

Well, it appears fixed! What bronxteck said made sense...but I was able to depressurize the system using the Tech2. I don't know how any of these one way flow valves work, but air was able to be removed when I tried depressurizing it.

I believe the issue was that when I followed the video with this new set up, I reversed the inlet sides. I had the right air bag connected to the solenoid for the left side and vice versa. With it previously being 1.5" out of wack from side to side, I think that was the cause of messing with the computer and the extended right height issue. After reversing the sides, I followed the recommendation to recalibrate the trim height. Since my driveway is sloped and I live in the mountains, I just did it in a (mostly) level parking lot I found using a jack on either side to level it out. It went well. It isn't perfect but appears to be within 1/4" of each other now....final measurements from the ground to the top lip of the fender flare is 42" and 42.25" (on newish factory sized Mickey Thompson Baja Boss mud terrain tires). My final normal voltages while sitting mostly flat in that parking lot is 2.49V and 2.55V. Extended height button now works correctly as well, both on the raise and deflate, and have readings of 3.33V and 3.37V. So I can confirm that even with the one way valves, this is a suitable fix if anyone has a inlet valve issue in the future and needs to replace it.

@oceanbrave I don't. I think I commented on your YouTube video awhile back where you clean the valve assembly. Mine was so horribly rusted, corroded, and cracked that it didn't improve after my cleaning attempts. I tried to seal everything up with epoxy as a last ditch effort but that didn't stop the leakage either. So I decided to follow this one way valve video as the last attempt to fix it before just switching to coils.

On to the next project!

 

Excellent - good to hear you got it working as it should!