2007 GL450 airmatic troubleshooting assistance - Mercedes-Benz Forum
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post #1 of 18 (permalink) Old 07-24-2018, 11:17 PM Thread Starter
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2007 GL450 airmatic troubleshooting assistance

Hi all, I have a 2007 GL450 with an airmatic issue that I could use some troubleshooting assistance with. Sorry for the long post but I prefer to give all the information I have and it helps me organize my thoughts lol.

Iíve been reading through the forums looking for things to check and am still not positive what the issue is. My nearest dealer is 150 miles away so driving there is not a good option, so I purchased an Autel meter to be able to read and reset the codes. The meter suggests the pressure release valve is faulty, but I know that doesnít necessarily mean that is the case. So in troubleshooting, I have:

1. Checked all 3 fuses. All are good.
2. Replaced the relay. Cheap possible fix, no effect.
3. Checked power to the compressor, didnít seem to have any, hence the relay replacement. I am not certain I measured the voltage correctly.
4. Checked for corrosion/broken wires going to the compressor/valve block, all appeared to be ok, but there appears to be heat damage to one side of the power plug. However, it does appear to still have a connection, albeit maybe not the most pristine.
5. Reset all codes via scanner, drove the vehicle for a day, then read the current codes. Only one for airmatic, as mentioned above.
6. Disassembled compressor/valve block assembly, all looks in order, more on this in a minute.
7. Checked for leaks, found none.

Now for the history. Car ran fine until one day the malfunction light cam on. It rode ok for a week or so then noticed it was riding really rough like it didnít have air or even springs. I jacked the car up to perform an inspection and after that the car started riding like it was ONLY on springs with no dampening at all. It felt like I was riding in one of those lowriders with the hydraulics active! Nothing I tried would get the suspension to air up, but somehow during my troubleshooting I noticed it was airing up and it leveled out to the proper level. I figured I must have done something that fixed it (without knowing what it was of course) and took it for a test drive. It malfunctioned again on the next drive, but it maintained pressure for two weeks, until I got brave and jacked it up again to perform brake maintenance. While the front wheel was up, I saw it rising (I noticed this the first time it bottomed out too) and now I am back to the lowrider again after putting it back on the ground. I have since been focusing on the compressor and valve block.

So one thing I noticed was any time I disconnected the air line between the compressor and the valve block, it was always pressurized. I also noticed that I have never been able to see/hear/feel the compressor run, and that has always sat in the back of my mind when I didnít seem to have power to the compressor. I disconnected the air line and left it off while I started the vehicle so that I could see if it ever put out any air. I discovered that it does not do so when it is supposed to, or when it is trying according to the dash, BUT when starting the vehicle, the compressor does it fact turn on and compress for 1-2 seconds.

So Iím having trouble deciding where to go from here. The compressor appears to have power, but doesnít seem to be turning on when it needs to. The scanner suggests the valve block, but when the compressor doesnít even seem to want to kick on when itís supposed to, I am reluctant to think that is it. Now I am starting to suspect the computer might not be sending the signal, but would think the scanner would catch that.

Ok thatís where Iím at. Thanks for reading and thanks in advance for any advice.
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post #2 of 18 (permalink) Old 07-25-2018, 02:35 AM
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Have you checked the condition of your level sensors as well? I find it interesting that the system aired up while it was jacked up to a certain level. Sometimes the arms can corrode and get stuck in place or can become disconnected. Thatís a good place to check as well.


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post #3 of 18 (permalink) Old 07-25-2018, 07:27 AM Thread Starter
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I inspected the level sensors and they appear to be in working order. There is no sign of corrosion that I can see, and although tight, the links rotate freely on their ball joints and do not appear to bind. The arm of the sensor raises and lowers with the tire. The scanner does not read any codes for the sensors.
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post #4 of 18 (permalink) Old 07-28-2018, 08:23 AM Thread Starter
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Bump...

Still trying to figure this issue out. Any thoughts are welcome.
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post #5 of 18 (permalink) Old 07-28-2018, 01:53 PM Thread Starter
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Originally Posted by james.calton1 View Post
Have you checked the condition of your level sensors as well? I find it interesting that the system aired up while it was jacked up to a certain level. Sometimes the arms can corrode and get stuck in place or can become disconnected. That’s a good place to check as well.


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James I just realized something you had mentioned; I may have been unclear on that point. The car didn't inflate when it was jacked up, I saw the tire rising after the car had been jacked up, and when it was placed back on the ground it was in the bottomed-out state. It's kinda weird, but basically I saw that airbag deflating while it was in the air.
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post #6 of 18 (permalink) Old 08-01-2018, 06:58 PM
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It wierd you posted this. This same exact issue has brought me here tonight. I have a 2008 gl450. Some days it will malfunction and than just raise back up and be normal. I found a code of 5505 once, cleared it and than got a 5507 code. Its totally random. I reset the code once and it drove headache free for a week. Than today the drivers side went down and malfunction light. This morning i expierienced exactly what you said about a lwrider lol. I think it is the valve block but unsure. I, like yourself see the compressor is pumping air, so i feel like that isnt it. Let me know if you figure it out!
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post #7 of 18 (permalink) Old 08-01-2018, 09:17 PM Thread Starter
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I got a new valve block in today and swapped it out, but the system still will not charge with air. If anything, the problem is worse now that I've released whatever charged air was in the system once I swapped over all the air lines. Is there anything special I have to do to reset the system when this component is changed out?

I'm really hoping somebody can assist me with this issue, I have now wasted $100 on a valve block I didn't need based on the information I had. I don't want to waste another $300 on a compressor I doubt I need, but all I can figure at this point other than that is it might be a computer problem.
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post #8 of 18 (permalink) Old 08-01-2018, 10:19 PM
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If you start the car and press the rise button, you should here the compressor engage. If it doesnt and it has power, to me that would seem to be your culprit. Also, are you sure none of the air shocks have leaks in them?
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post #9 of 18 (permalink) Old 08-02-2018, 07:53 AM Thread Starter
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Originally Posted by shadow00026 View Post
If you start the car and press the rise button, you should here the compressor engage. If it doesnt and it has power, to me that would seem to be your culprit. Also, are you sure none of the air shocks have leaks in them?
I am reasonably sure none of my airbags or lines are leaking. I did not go over the entire system, but I checked the most likely suspects (valve block, front airbags) and since no single corner of the car sits lower than any other corner, I have no reason to suspect a leak.

I know the compressor is getting power and runs, but I can't be sure it's getting power the entire time it needs it. It seems to work for 1-2 seconds upon startup which pressurizes the system just a little bit, but when the car is running and I push the rise button, it flashes that it is working, but the compressor does not turn on. I think this is where I'm most confused (and concerned). The compressor has power and runs, just not when it's supposed to.
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post #10 of 18 (permalink) Old 08-02-2018, 08:00 AM Thread Starter
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Now I did find one thing that seems anomalous, and I could convince myself that it could be the problem, though I don't know what to do about it. My Autel meter tells me the voltages of the level sensors and those do not match at all. I don't have the readings in front of me, but if memory serves, they are reading something like FL: 4.5V FR: 0.5V RL: 1.5V RR:4.0V

It seems to me like this could be the source of my problem, but I would think the system would just over- or under-compensate one strut or another to attempt to balance out the voltage inputs, not shut the entire system down, and the Autel meter does not suggest there is anything wrong with the level sensors.
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