2004 H2 spring conversion done and dead head air lines. Didn't remove any sensors and compressor keeps trying to raise the rear. Been working on the Hummer for 12 strait hours so might be a little delirious but I cannot locate the correct fuse/relay to shutdown compressor. Please identify.
Thank you.

 

Simply disconnect the compressor relay that is located near left front lower wheel well attached to chassis harness.

Should be a small square shaped unit.

(if you dont want the harness any longer, would you be interested in taking it out and selling it?? I'm thinking about installing my compressor for inflation uses only but I need the OEM harness with the relay and the 16 pin connector to complete the parts list.)

 

fyr145 thanks for the information. I will search for the relay after work this evening. Funny how there are a ton of threads on the issue but no specific location/identification of that relay...


When I find it I will post a picture for future reference.


I want to keep all the onboard air stuff in place for the same reason you do. I want to be able to use the compressor for onboard air. Just running out of time before my trip next month to mess with locking down the height sensors or anything else to keep the compressor from running....


Sign of relief actually as I thought it was a fuel pump going bad when I would pull into a store drive-through and hear the compressor ticking.

 

You're very welcome!

I have saved a bunch of wiring schematics and service manuals for our H2's so I can get an idea of where things are located.

The relay should pull straight out just like the ones in the under hood fuse box.

One of the wires goes to the leveling sensor that senses when the rig is not at correct height and turns on/turns off the compressor.

 

found the relay and pulled it last night. Its under the master cylinder attached about 6" up off the frame rail right behind the plastic wheel liner. Right where everyone said it would be.


I disconnected the negative battery cable before I pulled the relay but after I hooked the battery back up I got the "service Air system" message on startup. I didn't disconnect both battery cables and short them together (unattached from the battery!) so I may try that this evening. Took a pic but I didn't push it up to my webhost to post here so that will have to come later.

 

ok figured out how to make an album so here is a pic of the harness with the relay removed. Steering column is on the left master cylinder is just out of view upper right.

 

The BCM is detecting the removed relay and sending that warning message to your Driver Information Center (D.I.C.) on your dash. You may have to re-install the relay for now. Here is another work around that might help.

I went back and found a wiring schematic AND the owners manual to see if where exactly the relay is getting its power source from. I located the fuse that sends power to it, I was able to make a .pdf file for you to look at but the file size limits on this site wont let me upload it for you.

To get this schematic and fuse block diagram, just send me a PM on this site with an email address that you'd like me to send you these 2 files to. Then you can download them and print the out and take them to your rig and remove the correct fuse.

Worst case scenario if this workaround doesnt work, you might have to take it in to the dealer and have them connect it the BCM and have them turn it off. But lets try this workaround first to see if we can save you $$.

 

Thanks for the PM info. Will experiment tomorrow after work.
Thinking about this and I wonder if there is a way to mod the height sensors to always report perfect height and keep the compressor functional and the computer happy.

 

I just found a post that discusses this very same issue from another member, maybe this would work.


First, found out that one of my rear bags was about to fail (looked like it was sitting crooked under the truck), so I replaced them with coils.

Second, we left ALL of the electronics for the air ride suspension due to me wanting to still be able to use the rear cabin hook-up for tire inflation, etc.

Third, to avoid warning lights we unhooked nothing electrical. All my mechanic/buddy did was "dead head" the compressor.....in otherwords he cut the airline from the driver's side that was headed to the airbag and plugged it into the passenger's side compressor fitting.

Forth, the compressor (and all electronics therewith) are fooled into thinking the truck's rear ride height is always perfect. This also allows the rear cabin connection to still be used.

Fifth, only negative of this is that I loose the functionality of the rear "ride height" adjustment feature......very minor trade off (in my opinion) compared with the functionality of the coils vs. the bags.

Lastly, I have NO WARNING LIGHTS for the last 3 days and my compressor in the rear works perfectly and my coils are now bulletproof.

 

i get the service air system warning on mine every time i drive it. compressor still works, the ends are capped, i didnt do the removal so im not sure where.

any tips on what to look for to get it off? Compressor works and holds air, runs for just a second on initial startup then shuts off but then about 10 minutes into my trip, it comes on the dash.

thanks,
steve