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Recently installed a new compressor and ran the complete Star system pressure testing. The compressor kicks on driving much more than any of my other 3 air suspension systems did.
Today hooked up the Star system again … looking at the “Leakage test between valve block and central reservoir… At 20 minutes I dropped from 14.0 bar to 13.725…approx 3psi??? At 60 minutes staying at 17.725..Does anyone remember if there system was perfect and did not drop 0 ? Going to leave it hooked up for an hour or so…
Max I know you did an extensive writeup on the air suspension… Do you remember dropping anything ?
When I replaced the compressor a few weeks ago the air inlet hose was broken off at the compressor so I am thinking some dirt might have gotten into the valve block.. hate to replace with it passing all the test BUT it definitely is running too much ..
Last edited by vesiadog; Sep 21, 2025 at 02:48 PM.
Reason: wording
But this test is only about the leak between Valve Block to Central reservoir, just one from many pressure circuits from Airmatic, as is already stated on your picture the leak between Valve Block till any struts need to be checked with soapy water, also there is another hose from Compressor to Valve Block.
Anyway, the Central Reservoir is quit big so maybe in a few days will be balanced.
Last edited by trigital; Sep 21, 2025 at 02:53 PM.
All test pass and no leaks with the spray bottle… it just will come on going down the freeway? Fronts have 15k miles on them and rear bags look good …I am leaning towards replacing the valve block because the air inlet hose from the filter was torn open and I believe dust/dirt might have gotten into the block.
If all test pass, why you bother? The compressor fill the maximum pressure in the exact time Start test ask? Do that tests 3 times, with a little delay between test for compressor to cool down.
If this test fail, the compressor could be lazy.
The compressor AMK IS brand new… This is my third air suspension and my other 2 never really came on driving on the freeway. The suv sits up nicely after being shutoff all night… than 15-20 minutes into a trip the compressor comes on…compressor has run 98 minutes in the first 4 weeks…
The main reason is that you could have a poorly seated line from compressor to valve block and it’s really a bear to get in there. That would cause the compressor to have to run a long time to build the same pressure because there’s a leak in the line.
If your compressor is building pressure very fast per X entry, then start looking out the line between the valve block and the central Reservoir.
nothing happens in the system until you open or close a door, so for a central pressure reservoir to lose pressure overnight with no system activity would also indicate a leak or a disconnected line.
dirty valve blocks are rare because every time you open the door, the system cleans itself..
that whoosh you hear every time you open the door is pressure from the central reservoir being vented out through the compressor to the intake lane and out through the filter in the upper right fender to clear the system of any grit..
Last edited by Max Blast; Sep 21, 2025 at 07:41 PM.
As far as I remember, the systems are in and out meaning they pump air in and they relieve pressure to the atmosphere. They’re not just continuously recycling the pressure. The pump should run. You wanna make sure the pump does not constantly run or rapidly turn on and off on off.
If your line is connected properly, it should take about a second. If isn’t seated properly or has a leak in it like mine did on first installation, it’ll take about 5 to 10 seconds to get to 13 bar.
After putting in the new compressor I kept the fender well off.. installed the tire .. lowered it.. powered it up and took the tire off .. sprayed the block and lines with soapy water… everything looked great.
Example of driving today. After testing the unit with the Star system yesterday.. on startup the compressor ran for 5-10 seconds… when I pulled down the street the compressor ran for at least 20 seconds. After 50 miles I parked for 2 hours… compressor ran again on start up for 10-15 seconds.
The strangest part is I do not see the car dropping down at all.
Max do you think I should reseat the compressor line into the valve body?
I am definitely not use to hearing a compressor run this long…. thanks Bill
Yeah, I think your line from compressor to valve body isn’t fully seated in the compressor. Given the position and the amount of line you have available it’s going to fiddly and hard to do. Push what you got then give it a firm tug out and try again.
although taking the tire off makes it easier to reach, you don’t need to - you can just turn the steering wheel all the way to the right.
Searching for leaks… nothing. I decided to change the air valve body. Found a reliable ebay source for a German made Rapa for $133. With a little wrestling was able to change it without taking the bumper off .. fenderwell and engine bottom shroud cover and tire… on the 2 pt lift helped also.
Going to watch the compressor run time and pressure value with the IcarSoft over the next few days.. will hook up the Star system if it acts up again.. today after a few compressor runs at start up it stayed off.
I have no leaks and it passed every test … just everyday on the first road trip the compressor came on and than after every startup down the road. IMO it was acting like the tank pressure was leaking .. but had no visible leaks or sounds.
Ran the GL550 to the gun club (about 20 miles) compressor kicked on twice… Go back to last week .. the GL sat for 7 days and the suspension never dropped down. Today it passed every Star Airmatic test quickly… compressor test from 0-14 bar took approx 4 seconds .. very quick. Tested leakage from valve block to reservoirs .. not dropping at all .. even took it on the road during one of the reservoir test… dropped the tank guard and soap sprayed all three fittings and the two tank welds… no leakage.
The only possible item I am thinking is either a wiring or computer problem … possibly losing the reading of pressure and asking for more air pressure??? Of course this only happens on the road while driving not sitting in the drive or on the lift.
I had my son rock/sway the car during the valve block to reservoir test and the pressure went up from 14 bar to 14.137
I notice the same thing happened on my road test.. it went up from 15 to 15.12… most likely air from the bags going to the tank ??
If anybody has had similiar issues PLEASE post some thoughts… thanks Bill
I was not happy with FCP sending out an AMK by Arnott compressor… send it back and now have a Bilstein AMK compressor (new relay) also installed a used airtronic computer board (under driver seat) all same results. Next on the list will be all 4 corners leveling sensors. New german made valve body also.
The GL everytime starting ..as soon as the car hits 25mph (40kmh) the compressor runs for approx 10 seconds (even though before I leave the driveway the pressure is up and all 4 corners are good in heights )
The compressor will turn back on with in a few miles (for 10 seconds) and after that just a few burst 2-3 seconds (pretty normal) . If I shut the car off after the first or second 10 second run of the compressor… turn the car back on .. the cycle starts again ..25 mph and compressor runs for at least 10 seconds.
Following the flow chart both rear and front SAM are involved in the air matic system . CAN B&C bus signals.
Never a dash board error and both Sam’s have zero error and pass Xentry test .
This is definitely one of the hardest and longest troubleshooting spells I have been into with these 164 chassis. While doing lots of reading the 25 mph is the road wake-up for the system… The new Launcher handheld tester shows a lot of movements above 20mm which can bring on the compressor .
One local shop that spent some time on the phone with me said the SAMS should throw an error if they are involved??? Since the 4 levelers are showing a lot of movement … they are next on the list…
I am all ears for anyone having anything remotely the same.
NO LEAKS… PASSES ALL TEST via Launch or star.
No errors anywhere on the system… both under the seat of drivers and back hatch with rear sam are completely clean and water free. I have not looked at the front sam yet.
Both computer boards (original and used) act exactly the same. As soon as I shut the car off and start again same cycle of compressor…. I have even got out and measured the corners quickly and they are perfect height?????? The picture is the graph of level sensor movement .. once the hit 20mm in movement the system will ask the compressor to come on for adjustment … Not sure if the system is smart enough to know there is already a lot of pressure in the struts and bags…
Last edited by vesiadog; Oct 19, 2025 at 03:46 PM.
Whats the sensor saying that "tells" the system to lower when you get up to highway speeds? If its an actual sensor that it reads, maybe it is giving false data to the air system and its cycling the compressor at incorrect times. BUT if that system just uses data from the ECU, maybe look at that live data channel (whatever channel tells the Airmatic system the speed of the vehicle) and see what its saying at different speeds?
The following transient conditions apply to vehicles without code (430) Off-road package depending on the vehicle speed and the damping program setting:
From raised level into highway level
v > 70 km/h for t ≥ 20 s or
v z 90 km/h
In the Sport damping program, the system switches immediately from raised level to the high speed level.
The high speed level remains set as long as no level change is requested and implemented.
From off-road level 1 into highway level
v > 100 km/h for t ≥ 20 s or
v z 115 km/h
11 In damping program Sport, the system switches immediately from off-road level 1 to the high speed level. The high speed level remains set as long as no level change is requested and implemented.
From highway level into high speed level
v > 120 km/h for t 2 20 s or
v z 140 km/h
i In damping program Comfort, the system only changes to high speed level as of a vehicle speed of v > 160 km/h for tz 20 s or at v
≥ 180 km/h.
From high speed level into highway level
V < 40 km/h
From highway level into high speed level
v > 120 km/h for t ≥ 20 s or
v ≥ 140 km/h
i In damping program Comfort, the system only changes to high speed level as of a vehicle speed of v > 160 km/h for 1≥ 20 s or at v
≥ 180 km/h.
From high speed level into highway level
• v < 40 km/h
The following transient conditions apply to vehicles with code (430)
Tonight I tried another approach… I never use the raise and lower buttons. I hit the raise button and ended up with this ….
That is a good bit higher than I drive around 19.5” from center axle to bottom of fender well. The compressor ran for quite a bit but the very interesting part is once on the road and hit 25mph the compressor did not come on? It leads me back to believe that possibly the level sensors could be worn in the constant -25 to -35mm area? ( kinda of guessing at this point)
Will be interesting in the morning when I drive it to see once I hit 55mph if it lowers itself and than starts to act up again?????
I’m reading through this and I’m not sensing anything else wrong… If you’re wondering why the computer tells the compressor to kick on for about 10 seconds after you had 25 miles an hour all that sounds normal.
Also, be advised that when you and interrogate the airmatic unit, it actually locks out the system so you can’t really observe it with the computer. Only with your ears.
At this point, I would just leave it well alone and drive it for a while.
Thanks Max for reading thru a bunch of my post. If this was my first airmatic system I would agree .. just drive it. The compressor will not last long at this rate. Definitely a strange problem constantly asking the compressor to run… you are correct that once you start to read the airmatic values etc with an obdII reader you have shutoff the system … My thoughts right now are one of the 4 level sensors is asking to turn on the compressor …
The car sitting in the drive passes all test and has zero errors… just can’t have the compressor running 10-15 minutes on short 45minute drives… thanks again for reading all this stuff
Today at 25 mph the compressor is now running 35-60 secs… shuts off and comes back on for 30-40 seconds. The compressor has been installed roughly 3 days and has 30 minutes run time. I have driven my other air matic cars for many many miles and compressor might run 1-2 minutes. I am lost… the couple of shops I called said has to be leaking… the 0-14 bar test today took 4.6 seconds twice in a row. the car has zero leaks..
Has to be a few people out there that has seen this problem … I have been hooking up my IBDII readers to drive around so the pump gets some rest.
When I hook up my reader the car does not sag or lose pressure… I am lost… I am pretty sure the level sensors are going to be a waste of time also.
Last edited by vesiadog; Oct 20, 2025 at 06:31 PM.
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