Answer the 1Million Question: Where is the air ride control relay located?
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Cadillac Escalade, EXT and ESV Forum - 1999 - 2006 Discussion, Answer the 1Million Question: Where is the air ride control relay located? in Cadillac Escalade Forums; My friend has pretty much troubleshooted my no "compressor on" problem to the relay on my '02 EXT. We used ...
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    EXTodd is offline Cadillac Owners Member
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    Lightbulb Answer the 1Million Question: Where is the air ride control relay located?

    My friend has pretty much troubleshooted my no "compressor on" problem to the relay on my '02 EXT. We used a test light to the power (red wire) going to the compressor and we could not get anything. I stood on the back bumper trying to activate the compressor and we got no power. So I went to the local Autozone and the only info they had in the computer is that the relay is possibly located under the driver seat.

    It's a pigtail relay, Niehoff part # PS38281 "Accesory Relay Connector". It's a plug with 5 wires coming out of it.

    Can somebody please tell me where this is located in my 2002 EXT? Thanks in advanced.

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    250motorsportz's Avatar
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    Re: Answer the 1Million Question: Where is the air ride control relay located?

    I'd love to know the answer to this too.

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    EXTodd is offline Cadillac Owners Member
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    Re: Answer the 1Million Question: Where is the air ride control relay located?

    I'm making headway. If your Escalade is an EXT the Suspension Control Module is under one of the rear seats otherwise it's behind the rear right panel closest to the rear hatch. You have to remove the rear panel to get to it.

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    ewill3rd is offline Cadillac Technician
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    Re: Answer the 1Million Question: Where is the air ride control relay located?

    It should be located:

    On the left side of engine compartment near the Fuse Block - Underhood
    You might have to pull the housing off of the electrical center to see it.
    It should have a brown, light blue, and two red wires going to it.

    You need my paypal account info to send me the million?
    Let me know if you can't find it.
    You could still have other problems.

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    EXTodd is offline Cadillac Owners Member
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    Re: Answer the 1Million Question: Where is the air ride control relay located?

    Quote Originally Posted by ewill3rd View Post
    It should be located:


    You might have to pull the housing off of the electrical center to see it.
    It should have a brown, light blue, and two red wires going to it.

    You need my paypal account info to send me the million?
    Let me know if you can't find it.
    You could still have other problems.
    Thanks ewillr3d! Are you saying it's the big fuse box or below it? Do you have a diagram that you could post? Thanks bro, I know I appreciate this a lot and I'm sure many others here do too. Is this where the actual relay is? Do you know the part # for the relay?

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    ewill3rd is offline Cadillac Technician
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    Re: Answer the 1Million Question: Where is the air ride control relay located?

    I don't know the part number, I tried to find a picture but I couldn't. I don't have any in the shop right now.
    There is a plastic cover over the main fuse block under the hood, sometimes the relays are mounted close by, sometimes they are under the cover.
    To remove the cover, remove the left side frame brace (four 13mm head bolts) and then release the hook tabs down on the sides of the cover, pull it up and look for the relay.
    There could be a couple mounted there, just check the wire colors for your relay. It should have a number on it.

    Our relays don't really fail that often, be sure to check the maxi fuses and related system fuses in the main fuse block.
    The relay (power to compressor) is fed from the "stud 1" fuse and the "ign 3" fuse feeds the control side of the relay.
    lcavalier and lcavalier like this.

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    EXTodd is offline Cadillac Owners Member
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    Re: Answer the 1Million Question: Where is the air ride control relay located?

    Quote Originally Posted by ewill3rd View Post
    I don't know the part number, I tried to find a picture but I couldn't. I don't have any in the shop right now.
    There is a plastic cover over the main fuse block under the hood, sometimes the relays are mounted close by, sometimes they are under the cover.
    To remove the cover, remove the left side frame brace (four 13mm head bolts) and then release the hook tabs down on the sides of the cover, pull it up and look for the relay.
    There could be a couple mounted there, just check the wire colors for your relay. It should have a number on it.

    Our relays don't really fail that often, be sure to check the maxi fuses and related system fuses in the main fuse block.
    The relay (power to compressor) is fed from the "stud 1" fuse and the "ign 3" fuse feeds the control side of the relay.
    Yeah, STUD1 is the first fuse I checked and it's good. So you're saying the relay is actually under the main fuse block under the hood? Bellevue, WA Cadillac helped me locate the actual relay today and I bought it from them. tyco brand, part # 12193601. It's the same basic relay for the fuel pump, A/C, etc. Nothing special. Yeah, $40 for a relay is dumb but they printed out the schematics and really tried to help me. Even the service tech could not tell me exactly where the relay was either, he was stumped. He thought it may be by the SLC unit in the rear passenger side panel behind the seat. But I think you are probably correct as most relays are at or around the fuse block.

    I'm going out to the EXT shortly so I will check back here and tell you what I find.

    Yeah, I'll prolly owe ya $1M so I need your PayPal info.

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    Re: Answer the 1Million Question: Where is the air ride control relay located?

    Well first off the dude at the service counter was wrong about that being the same relay as the fuel pump, A/C, etc. Different sized relay, not the same at all. The relay I got today is larger. tyco brand, part # 12193601. I did notice the relay I bought has a sleeve molded into one side of it so it can be mounted onto something. So I would assume that it doesn't go in a fuse block.

    Ok, out to the EXT......

    I'm back....

    I did find a similar relay mounted to the side of the plastic housing at the bottom of the fuse box. Just like ewill3rd said. I thought this may be the same part but I read OEM part # 12193503 off the relay. What is this one for? So I suppose my next step is to take the support brace off and lift the fuse block plastic housing as ewill3rd instructed me.

    ewill3rd, did we troubleshoot this correctly? We didn't pull any codes from the computer with the OBD2 reader. We tried to activate the compressor and we used a test light to see if there was current. We got nothing. Last Sunday when I was in the house getting something my buddy was outside troubleshooting and he swears he heard the compressor kick on after turning the ignition to on. He yelled to me and I ran outside and it stopped before I got out the door. I would lean to believe him because he knows more about cars than me and he also owns a Chevy Trailblazer with the same air ride system. So he knows the sound of the compressor.

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    EXTodd is offline Cadillac Owners Member
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    Re: Answer the 1Million Question: Where is the air ride control relay located?

    I believe I also found the suspension control module and something else under the rear driver side seat with a plastic housing around it. The larger aluminin cased ECU looking device must be the SLC? It says Delphi OEM Service # 15081997. There is also a smaller black plastic unit to the side. It says Bosch # 15068175. What's this?

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    EXTodd is offline Cadillac Owners Member
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    Re: Answer the 1Million Question: Where is the air ride control relay located?

    Quote Originally Posted by ewill3rd View Post
    It should be located:


    You might have to pull the housing off of the electrical center to see it.
    It should have a brown, light blue, and two red wires going to it.

    You need my paypal account info to send me the million?
    Let me know if you can't find it.
    You could still have other problems.
    Yeah, those are exactly the wire colors that I saw but going into a blue tyco relay #12193503. Did the parts guy give me the wrong relay or are these relays interchangable? He gave me a black tyco relay #12193601. Looks like the same size.

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    ewill3rd is offline Cadillac Technician
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    Re: Answer the 1Million Question: Where is the air ride control relay located?

    Wow, sorry I am not keeping up with you...

    The parts catalog is pretty worthless when looking up relays sometimes. Usually I find the relay I want to replace and give them the old number to get the new one.
    It shouldn't be the same as a fuel pump relay.
    If the exterior dimensions are the same it will plug in but sometimes the circuitry and contacts inside can be different based on the usage. One might hold up to more switching current than another.

    As for diagnosing it, there are steps you should take. I can give you a couple ideas but I am not sure if that will completely diagnose the problem.
    Any controlled relay is easy to check, provided the criteria are met for activation.

    For example, to drop voltage straight to the compressor to see if it will come on you could use a jumper wire from one of the red wires to the other.
    That is what the relay does when it is activated. It should dump power to the back so you can check with a test light to see if the wires are broken under the truck somewhere.
    You can use a test light to check for voltage on the control circuit (brown wire), do you still have the schematics?
    The suspension control module grounds the blue wire to activate the relay. You could backprobe the blue terminal with the relay connected, it may provide enough of a ground to activate the relay and if everything is connected you should hear the compressor kick on.
    The module under the rear seat is indeed the suspension control module and it is in charge of the level ride.

    Realistically you could have issues with the height sensor, wiring, module, or the compressor itself.

    Based on what you have posted so far I would say jumper from red to red at the relay and see if the compressor comes on and go from there.
    I don't see many failures on that system so I can't really tell you where to go based on a high failure rate of any particular part.
    I might only have a chance or two to check back today so I apologize if I can't get back to you quickly but I'll check back if you have more questions.

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    Re: Answer the 1Million Question: Where is the air ride control relay located?

    Hey, thanks a lot ewill3rd. I will do as you say as soon as I can get some time. Probably this Saturday. You have given me great information and I am thankful.

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    ewill3rd is offline Cadillac Technician
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    Re: Answer the 1Million Question: Where is the air ride control relay located?

    You are most welcome.

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    EXTodd is offline Cadillac Owners Member
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    Re: Answer the 1Million Question: Where is the air ride control relay located?

    Quote Originally Posted by ewill3rd View Post
    Wow, sorry I am not keeping up with you...

    The parts catalog is pretty worthless when looking up relays sometimes. Usually I find the relay I want to replace and give them the old number to get the new one.
    It shouldn't be the same as a fuel pump relay.
    If the exterior dimensions are the same it will plug in but sometimes the circuitry and contacts inside can be different based on the usage. One might hold up to more switching current than another.

    As for diagnosing it, there are steps you should take. I can give you a couple ideas but I am not sure if that will completely diagnose the problem.
    Any controlled relay is easy to check, provided the criteria are met for activation.

    For example, to drop voltage straight to the compressor to see if it will come on you could use a jumper wire from one of the red wires to the other.
    That is what the relay does when it is activated. It should dump power to the back so you can check with a test light to see if the wires are broken under the truck somewhere.
    You can use a test light to check for voltage on the control circuit (brown wire), do you still have the schematics?
    The suspension control module grounds the blue wire to activate the relay. You could backprobe the blue terminal with the relay connected, it may provide enough of a ground to activate the relay and if everything is connected you should hear the compressor kick on.
    The module under the rear seat is indeed the suspension control module and it is in charge of the level ride.

    Realistically you could have issues with the height sensor, wiring, module, or the compressor itself.

    Based on what you have posted so far I would say jumper from red to red at the relay and see if the compressor comes on and go from there.

    I don't see many failures on that system so I can't really tell you where to go based on a high failure rate of any particular part.
    I might only have a chance or two to check back today so I apologize if I can't get back to you quickly but I'll check back if you have more questions.

    I did what you said ewill3rd. You are correct, the compressor kicked on when we jumped red to red. So what we did was install a push button switch into the fuse block and t-spliced into the blue wire and grounded it at that support brace right above the fuse block housing. We concluded that the relay was good because we ran power and ground where red to red connects (@ pin 30 & 82) on the relay and it clicked (opened). So we are thinking it may be the ride height sensors causing the issue? If it was the suspension control module wouldn't something show up in the message center and wouldn't we get a code when we scanned it with the OBD2 reader?

    Ok, even when I manually start the compressor and let it run it doesn't load air into the rear shocks and raise the rear end. I hooked my boat up to the hitch to add weight and I ran the compressor for a few minutes straight and it did nothing at all. All I hear is the compressor running and that's it. Is there a valve to the air shocks that is controlled by the suspension control module? Are my shocks shot? If the shocks were bad wouldn't the truck sag at the rear?

    I am now totally confused because I thought we at least manually overrode the system to at least make it possible to tow the boat this weekend. I want to fix this right and have the ALC work normally. We will take the rear wheels off and adjust or replace the ride height sensors because we're thinking that is where the problem is. I just want to know what to buy because I am ready to fix this problems once and for all. I will buy new rear shocks from Arnott or whatever is needed. I just needs some insight and help here guys cause I thought we had a work around today but we're no better off than we were a few weeks ago. We can hear the compressor running when we push the button now but nothing else.

    Thanks for all your help ewill3rd. I still need your expert advice cause I am at another road block.

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    ewill3rd is offline Cadillac Technician
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    Re: Answer the 1Million Question: Where is the air ride control relay located?

    Do you know how to remove the air lines from the shocks?
    If so you could see if there is any pressure getting to them. You could run the risk of having the truck sit lower if the compressor is not working and there is pressure in the system.
    Even though the compressor may run there is still an exhaust solenoid in there, it could be stuck open or some variant.
    I'd have to pour over the schematics to see what could be your issue otherwise. I'd say the relay is probably fine based on the testing you have done so far.
    It might be hard for me to try to find time to help you further but if you want I'll sure try.
    Just bump this topic a couple times and I'll see it as a reminder. If you don't hear from me send me a PM.

    I'll have to see what kind of tests you can do without a scan tool.

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