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2003 E320 4matic wagon; 1979 450 SL
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Discussion Starter #1
2007 E3504matic wagon, air matic in the rear only. Been losing pressure over about 48 hours. Especially in colder weather. Had the system scanned by my Indie. He came up with# 5350 stored/ A91y1, Airmatic pressure release valve; open circuit. I was thinking I had maybe a small leak in a line. Where is this pressure release valve located?? Any help appreciated..Thanks
 

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E320/E250 Bluetec Ford F350 6.7l
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Lot of members experienced torn wires at the compressor, so that is what you should check first.
Still open circuit on relief valve will not trigger air leak, meaning you have more to check.
 

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2003 E320 4matic wagon; 1979 450 SL
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Discussion Starter #4
Konigstiger, Thanks for the pics and diagrams. Those are great. Kajtek, agreed, the note about broken wires really caught my eye. We had a really big wind storm in October and I had a big tree limb fall right across the front of the hood, which most impact right over the location of the compressor. Actually that was when I first noticed problems....But, I also had just purchased the car and figured I got suckered on that one.
 

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2003 E320 4matic wagon; 1979 450 SL
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Discussion Starter #5
Also, hoping to make it a few more weeks till warmer weather..
 

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Discussion Starter #6
Update, I checked the compressor and wiring. Checked for leaks everywhere I could get at. I didn't find any leaks. There was the suggestion that probably both air bags were leaking. Then, the car went from rear end sagging a small bit over night, to bottoming out overnight. I assumed the bags must be shot. Ordered the spring conversion kit and it arrived Wednesday. But now the car has sat since Tuesday and has not dropped a bit??? Now, I'm thinking it must be a sensor. The airmatic diagram for this car lists one sensor in the rear. It lists the control unit up front. Is that the electronics under the carpet in the passenger footwell? Or, is there another sensor on the outside underneath. It would be easier if I had a lift, but I'm doing this on the ground. with the car jacked up... Thanks
 

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2003 E320 4matic wagon; 1979 450 SL
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Discussion Starter #7
So, if I understand this system correctly. On a rear air only self leveling system. There is a sensor in the rear that signals the air springs to open or close to adjust height and correct. Does the air exit the spring through the same valve that it enters. And then through the piping up toward the compressor and out through the pressure relief valve.? Does the sensor in the rear route it's signal through the electrical components located in the passenger footwell?
 

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'71 Pinto
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Revisit compressor lines, rear axle distributor, and air springs. Absolutely no visible leaks – IMHO colder temperature related problem = compressor internal moisture Airmatic compressor service/rebuild - MBWorld.org Forums , line to rear failing, or air springs internal leak.
 

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E320/E250 Bluetec Ford F350 6.7l
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So, if I understand this system correctly. On a rear air only self leveling system. There is a sensor in the rear that signals the air springs to open or close to adjust height and correct. Does the air exit the spring through the same valve that it enters. And then through the piping up toward the compressor and out through the pressure relief valve.? Does the sensor in the rear route it's signal through the electrical components located in the passenger footwell?
The compressor pumps air into the main line and each air bag has individual valve to regulate air.
So the differential -mounted sensor gives signal to open the bags valves and when pressure in the line drops, the compressor kicks in.
The program has time-outs to prevent compressor overheating.
When level become too high, the computer opens the dump valves on front of compressor and bags valves at the same time. This way return air blows the water from dryer.
Now with any leaks, there is no return air and whole systems gets flooded with moisture.
If you find a way to read the line pressure, you will narrow troubleshooting to line problem v/s bags problem.
When I had leak in the system and affordable scanners were not available at the time, I T-ee the 4 mm air line and add pressure gauge to monitor what's going on.
That also allowed me to hook up shop compressor for finding pinhole in the tubing.
 

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2003 E320 4matic wagon; 1979 450 SL
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Discussion Starter #10 (Edited)
Konigstiger and Katjek1, thank you both for hanging in with me on this. Just trying to make sure I understand how system works. Konigstiger I also felt it was cold weather related , but we have had nights in the 20's the last week or so and no leaks. The only thing I found was when I checked the compressor, The rubber line that goes between the air filter and the compressor had a good size crack in it and it was hanging down. I did not replace the hose yet, but I did tywrap it up in place so it wasn't hanging and that may have closed up crack. So, entirely possible moisture related. I will monitor and continue to investigate and keep you informed. Lousy weather for next few days though. Also great idea on the pressure gauge....Thanks again
 

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Update, I checked the compressor and wiring. Checked for leaks everywhere I could get at. I didn't find any leaks. There was the suggestion that probably both air bags were leaking. Then, the car went from rear end sagging a small bit over night, to bottoming out overnight. I assumed the bags must be shot. Ordered the spring conversion kit and it arrived Wednesday. But now the car has sat since Tuesday and has not dropped a bit??? Now, I'm thinking it must be a sensor. The airmatic diagram for this car lists one sensor in the rear. It lists the control unit up front. Is that the electronics under the carpet in the passenger footwell? Or, is there another sensor on the outside underneath. It would be easier if I had a lift, but I'm doing this on the ground. with the car jacked up... Thanks
i ran into the same issue and code. Front wouldnt fill, rear would sag after some time. cold weather wasnt helping as well as the same fault code.

I checked all wiring/volts which were perfect, replaced both front airmatic struts, i replaced the compressor and valve block, still no luck.

what i ended up doing to fix this issue is pretty stupid. I cut off the electrical plug that goes into the compressor or valve block, cant remember which one but i remember it did have 2 wires and it was "D" shaped i believe, and i soldered them on directly to the compressor. Cleared all codes and viola, it worked for me. there must have been just a bad connection or something. You should try it and let us know! I wish someone wouldve told me that before spending all the money on everything i didnt need, just 10 minutes to cut the wire and solder it lol

Even if the plug and wires look perfect and give out the right volts, i'd still give it a shot becuse thats what i had to deal with. It was a 2005 E500 .
 

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Discussion Starter #13
Thanks, am in the process of checking all wires..Thanks again
 
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