Service Air Suspension...Again!!! HUMTECH

[14u2nv2]

Started getting the "Service Air Suspension" message intermittently, but the air suspension still inflated and maintained ride height when the truck was running.

Sometimes (but not always), when the truck was parked overnight, the air suspension would deflate overnight, but would re-inflate as soon as the truck was started.

A few days ago, whenever I started the truck, the compressor would run for about 30 seconds and shut off and the "Service Air Suspension" message came on without raising the suspension (sitting on the bump stops). Every time I start the truck it does the same thing, and the compressor only runs for 20-30 seconds and does not raise the suspension (either side).

The compressor seems to be working OK and the air port/hose work when I switch the air compressor on with the switch in the rear of the truck.

I bought new air springs, since the truck's a 2003, and figured it's about time to replace them anyway. When I pulled the driver side air spring, I checked it for leaks and it had a very tiny leak--not enough to cause the problem, so I checked the air line while the compressor was running and no air was coming out of the line on the driver side.

So I bought a new driver side height sensor and still no luck. Nothing has changed and I still have the same problem. No air coming out of the driver side air line and the compressor shuts off after a few seconds.

My local dealer, that used be a Hummer dealer is now just a Cadillac dealer and seems to be a little clueless. The nearest hummer dealer is about 30 miles away and I don't want to drive the truck too much on the bump stops.

I know that the ride height needs to be calibrated after a sensor change, but is it possible that it would not work at all with a new sensor until calibrated?

I can get a new compressor for about $400 and am tempted to do this, but that won't solve the problem if it's a calibration issue.

Any other tricks to dianose this?

Any help is greatly appreciated,

John

[Planohummer]

1)there's a recalibration out for ECAS module-have your dealer do it. should cost less than $100

2)There's an updated design compressor available.

most common failure is exhaust solenoid or overtemp fault. You can't get parts from GM, gotta buy the whole compressor. The compressors are made by Trelleborg - UK division, they might sell you components.
http://www.trelleborg.com/en/Automotive/

[Easy Ed]

Hope it is not the air inlet filter that the services manual does not mention.

Post Link http://www.elcovaforums.com/forums/s...air+suspension

I think this may have been the problem. would have changed it if I knew it was stuck up and under the drivers rear fenderwell Restricted air flow to the compressor, caused it to heat up and shut down til the next start up and then all over again.
Attached Images

[HUMTECH]

If the compressor runs for 20-30 seconds without a height change it will set a code and disable the air ride. If your positive you have no leaks it sounds like the compressor may be too weak to inflate the springs. As easy Ed said if the inlet filter is plugged this could also be the problem, no inlet air=no output from compressor. Check the filter, if its plugged remove it and see if it works. If thats not it try to raise the rear of the body a few inches with a jack under the receiver hitch and see if the bags start to inflate, if so the compressor is jus weak. If all that fails a new compressor is likely in your future, the new compressor will need to be upfitted with new air lines as well if you still have the older single stage unit. Make sure these are ordered with the new unit.

[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

[jarek m]

Ok so we just got back from our NEW dealer, the diagnoses is "lack off base line for trim control". He cleared the codes and enabled the system back up for the ride home. Wednesday we go back for System and trim reset. $110 pr hour x 2 hours (he says) still comes to $ 250 with tax, good news!!!

[fbodyguy99@hotmail.com]

what made you think you should change driver side sensor? did you have it scanned and if so what codes came up maybe i can help