Service Air Suspension...Again!!! HUMTECH

[14u2nv2]

Thanks to everyone for your replies...

Planohummer,

That's kinda what I thought it might be--a problem with the valve block/exhaust solenoid on the compressor assembly.

How long would it take to trigger an overtemp fault? The compressor stops in 20-30 seconds on it's own, but if I turn it on with the switch in the back of the truck (onboard air/hose) it stays on as long as I like. Wouldn't the compressor overheat and trigger the overtemp fault while using the switch/hose in the back?


Easy Ed,

I read your other post where you posted that photo of the filter and that was one of the first things I checked. My truck has a ceramic style filter and it looks OK.

How long did your compressor run before it shut down? Was your onboard air hose working and did the compressor stay on while you had the switch in the back turned on?


HUMTECH,

I had the driver side air line disconected from the air spring and the truck lowered all the way(to make the sensor think it needed to be raised)and no air was coming out of the air line(to air spring) while the compressor was running.

Is it possible that the new sensor is so far out of calibration, that it thinks the truck is too high(even when lowered all the way)?

Do you know the part# for the air lines if I convert from the old model to new model compressor?

By the way...Thanks for the tip you posted about rerouting the harness to the new version sensor. You saved me $150.


Thanks again,

John

[Easy Ed]

"My truck has a ceramic style filter and it looks OK" That is a bonus.

"How long did your compressor run before it shut down" Less than a minute, I think, been a while.

"Was your onboard air hose working and did the compressor stay on while you had the switch in the back turned on?" Nope

Good luck with yours, Ed

[HUMTECH]

If the compressor is running it is trying to inflate the bags so calibration is not an issue. Is there air going to the other line? if not i would say your compressor is hooped. I dont know the part numbers but any gm dealer should be able to find them, there should be a note in there catalogue for required parts when upfitting the dual stage compressor in place of the single stage unit

[14u2nv2]

I haven't checked the other (passenger side)line, but there is some pressure in the air spring, although that side isn't raising either. The driver's side air spring was completely empty before I removed it and had no pressure. I'll check the other(passenger side) line tomorrow.

Can you tell from the photo if this is the newer two-stage compressor or the older single stage...





Thanks again,

John

[Planohummer]

that's the original single stage.
the amount of pressure for lifting the truck is a whole lot more than what's at the rear aux port. This may be why the pump runs ok when it's not lifting the truck.
You really need to check the DTCs before you spend any money-make sure it's not just a height sensor recal issue or something similar. Any GM store can ck the codes for you, when you get them post them on the forum and we'll decipher.

[jarek m]

Believe it or not I had the same thing happened today:

Symptoms
- service air suspension light
- compressor runs for 20 seconds at start up
- rear end does not come up
- passenger slightly inflated
- driver side empty
- no air coming from driver side line

Already checked
- inflation system goes to well over 100psi
- driver side air bag has no leaks
- both sensors have been recently replaced
- air compressor has been changed year ago
- disconnected the battery for a while with no effect
- raised the body and cycled the compressor without driver inflating or passenger changing air pressure


Mine happened after towing my other SUV for couple hundred miles. Also ever since two years ago I changed one of the air bags then in little while each of the sensors then the compressor I never reset the system, my dealer claims there is no such a procedure!!!(Gold Coast Hummer Dealer)

[HUMTECH]

Well the procedure is lift the rear of the truck, and install the calibration blocks between the bump stop and diff housing (every Hummer dealer should have these as an essential tool) depressurize the air suspension system. With the tech 2 go to chassis, air suspension, special functions and then trim height learn. If everthing is good trim height learned will be displayed. raise the rear off the calibration blocks and remove them. close all doors, run truck and verify system works.