Air Ride Compressor Issues

[SteveC-VA]

I am new to this forum but have been searching multiple forums for info on my issue. I am pretty handy and do most of my own vehicle maintenance, have a herd of 7 different vehicles, the 2007 Yukon XL Denali being the one in need of help. I noticed my highway ride had become bouncy and sort of floating so I suspected the air compressor had gone out again. I bought the truck in June of 15 and it had a very noisy compressor, I had to change it shortly after I bought it and it worked fine for a while, I noticed it had stopped working about 4 months ago. I ordered a new Arnot from RockAuto and put it on and still would not work. I started checking the fuses and connections and still cannot find the issue. I put 12v right to the compressor, old and new and they both turn on, with the unit installed,I get a single click at the compressor when I turn the key to the run position, same indication if I start the truck. I have removed and cleaned the ride level sensors on the rear and tried to take resistance readings on them but not sure what I should see between the pins on the sensor. I haven't been able to find much info on them and don't want to just change them out at 60-120 dollars each. I am not getting the 12v at the body side connector at the rear so I checked the relay under the hood and not seeing it there. I have checked all the fuses I know to check and they are good. I want to ask if anyone has a good schematic that I can download to use in tracing out the wiring to see where my voltage or control signals are being lost.

 

[kbuskill]

I am new to this forum but have been searching multiple forums for info on my issue. I am pretty handy and do most of my own vehicle maintenance, have a herd of 7 different vehicles, the 2007 Yukon XL Denali being the one in need of help. I noticed my highway ride had become bouncy and sort of floating so I suspected the air compressor had gone out again. I bought the truck in June of 15 and it had a very noisy compressor, I had to change it shortly after I bought it and it worked fine for a while, I noticed it had stopped working about 4 months ago. I ordered a new Arnot from RockAuto and put it on and still would not work. I started checking the fuses and connections and still cannot find the issue. I put 12v right to the compressor, old and new and they both turn on, with the unit installed,I get a single click at the compressor when I turn the key to the run position, same indication if I start the truck. I have removed and cleaned the ride level sensors on the rear and tried to take resistance readings on them but not sure what I should see between the pins on the sensor. I haven't been able to find much info on them and don't want to just change them out at 60-120 dollars each. I am not getting the 12v at the body side connector at the rear so I checked the relay under the hood and not seeing it there. I have checked all the fuses I know to check and they are good. I want to ask if anyone has a good schematic that I can download to use in tracing out the wiring to see where my voltage or control signals are being lost.

Have you checked fuse 54 Automatic Level Control Compressor Relay.

I believe there are a couple other fuses related but can't remember them off the tip of my head.

You said you checked the relay but did you try unplugging the relay and applying 12v to see if the compressor kicks on?

There is also the possibility that the ESCM has gone bad or has a problem but I would check the simple things first.

I remember there being a fuse in the fuse panel at the end of the dash that had something to do with it as well but again the truck isn't in front of me to look at so perhaps someone else will chime in.

If the compressor clicks when you turn the key on then it sounds like it's getting the signal to open the exhaust valve but then not getting the power to turn on.

A Tech2 would be extremely helpful to troubleshoot this system.

 

[SteveC-VA]

Thanks for the response. I did check #54 and it is good. I haven't found any fuses blown for any circuits. On the relay, I removed it and I do have the 12v on the plug for the relay, I jumped that across to the output side of the plug and it still didn't turn on. I checked all the dash panel fuses again this morning and all tested good.

 

[Doubeleive]

did your arnott pump come with a new relay? when I bought mine a few months ago it came with a new relay that connects on the harness leading up to the fuse box under the hood

 

[SteveC-VA]

It did come with a new one, it was put on when I changed the compressor. Just to be sure, when the new compressor wouldn't come on, I tried the old relay, no luck there either.

 

[kbuskill]

Thanks for the response. I did check #54 and it is good. I haven't found any fuses blown for any circuits. On the relay, I removed it and I do have the 12v on the plug for the relay, I jumped that across to the output side of the plug and it still didn't turn on. I checked all the dash panel fuses again this morning and all tested good.

So you do have 12V at the relay plug which means it's not a fuse.

So it's either not getting the signal to close the relay... easy enough to check... hold the relay while someone turns the key to run and wait about 10 seconds to see if you hear/feel it click.

Or there is a break in the wire leading to the compressor.

I would probably connect 12V to the relay connectors output side and check for voltage at the compressor end of the harness or if you have a long wire you could plug it into either end of the harness and run it up near the opposite end and check for continuity.

You could also check for continuity to ground which it should not have but if it did that means you have a dead short to ground. If this were the case then it "should" pop the fuse though.

 

[Doubeleive]

I have seen some other people mention there being a issue with the harness connectors at the air pump, you might want to have a good look at them and see if any pins look pushed in or for any signs of corrosion, the pump should release air and then kick on for a few seconds every time you turn the key to the on position, this would be regardless of any ride height sensor it is a self check if it is not doing that I would suspect that relay as ken mentioned you should be able to hear or feel it "click" but even then it could be faulty, you may be able to get a replacement at the auto parts store if it is questionable, just take the old one with you to match it up.

 

[SteveC-VA]

I do have 12v at the relay plug, that's what I mentioned in an earlier post, I jumped that over to the output side of the plug and still didn't work. I did check the relay when I turn on the ignition, I can hear the click on the compressor and then I feel the relay click and then about 5-10 seconds later it clicks again, I suppose the two clicks are when it energizes and the other when it de-energizes. I'll take the harness from the old unit I just pulled off and cut it to be able to directly apply 12v to the compressor from the relay. Thanks for the input.

 

[gpracer1]

This is one of those situations where you need to find someone with a tech 2. You can command the pump and see all the shocks and sensors.

 

[SteveC-VA]

I tried the work around with the wire going from the relay directly to the positive wire on the compressor and it worked. I released the air pressure from the system and reconnected the plug and no joy. I pulled the plug apart and looking closer I saw what is in the pic. The positive terminal was slightly melted and not making contact. Long story short, I pulled both pins from the plugs and hooked them directly together outside the plug and shrink wrapped then taped it up, temp fix. Now I need to source a new plug to fix it correctly. Thanks to all for the leads and getting me thinking a little more out of the box.