Sirdoogles

Currently my W164 ML320 with 154k miles that I love very much has been running into issues with the Airmatic system. Firstly, the air compressor runs intermittently when I'm driving for like a second or two, and always runs for 30 seconds when I hit 25 mph for the first time. Adjusting the ride height seems to be functional but setting to the 'raised' setting raises the vehicle but the compressor does not want to stop. Setting the Airmatic to lower again turns of the compressor and lowers the vehicle like normal.
The vehicle seems to lower to a normal elevation when it is parked. Doesn't looked like a slammed S or M class like I've seen on other forum photos with leaky Airmatics. however during the self-leveling process I have noticed that the rear ALWAYS seems to be at a higher position than the front with a hissing noise louder that I would like it before the front & back evens out.

Thanks to the other threads here I have checked the following:

• Airmatic Valve block (Factory original, but still holding up, used soapy water)
• Air Springs (Only front passenger air spring replaced W/ Arnott, rest are factory. No clearly visible damage, used soapy water, no bubbling but still suspicious of the components)
• Fuses and Relay for Airmatic system (All work good)
• Air compressor, (Replaced earlier in the year)

When we checked the air springs, we forgot to check the ride height sensors, which now I suspect the sensors may be damaged. My hunch is that the rear sensor(s) are faulty, which signals the vehicle to raise the rear higher than the front like it's anticipating a trailer load. Still doesn't explain the intermittent running of the compressor or that it is constantly on when the vehicle is raised fully. It is entirely possible that there is still a leak somewhere and completely missed it, but it feels like there an electrical issue to this problem as well too. I'm going to put this on our car lift soon and check out the rear ride sensor.
Would anyone know the exact location of the sensors and confirm that there is 1 rear ride height sensor or 2 for each rear strut? Thanks in advance, I know Airmatic issues are super common but I really don't want to replace another compressor and just want to spend the time to fix this current issue! Any other advice is welcome too!

Maj. Dundee

You should have the codes read in Airmatic or every else will be guesswork.

Sirdoogles

Thank you alot for the document! I only have a OBDII so either I will have to go to a independent shop in my area for the codes or get an SDS myself. Any good recommendations for a decent SDS clone?

Maj. Dundee

esphil

I just received this one a few days ago.

https://amzn.to/3kGhWhJ

Its been great so far, I have a random air suspension malfunction and it showed me that there was apparently a issue with my right front wheel speed sensor. It should show you everything you need to find about the air suspension system. When you say the relay works good what do you mean? I HIGHLY recommend replacing the air suspension relay with a new one. I just ran into this issue with the relay would stay on randomly after the car shuts off. You can't tell if its working right or wrong by looking at it. Its internal, its better just to replace it all together. This is the one I purchased.

https://www.ebay.com/itm/For-Mercede...72.m2749.l2649

You can look at the relay and tell if its original too, I think the old ones are Tyco maybe? New one should be hella, don't go aftermarket relay either to save $. That scanner should tell you exactly what fault you are running into. It also shows live data showing the height of each sensor. So you can rule out if theres one showing a bad reading or no reading.

Sirdoogles

I checked the respective relay for the airmatic system. They are indeed Tyco, and not the the Hella everyone recommends. The relay for the ignition also uses the same Tyco relay part # as well. What I did was a really lazy test was to swap the relays for the starter and the airmatic since they are the same. My hypothesis was that if the airmatic relay is bad, then the vehicle will either struggle or not start at all. However, car started without effort. This was done before I got the scanner, the same one you mentioned.

So now with the scanner, I'm going to see what is causing the specific fault codes and update you guys here. Honestly, I should of gotten this device sooner. It will also help with our W211 CDI as well.

Afterwards, I'll just source what components I needs via FCP Euro or my local dealership.

Maj. Dundee

Post the codes first before you buy any parts.

esphil

The thing is even with a bad relay things may still function, but have sporadic faults. Mine would be off and on, and the pump wouldn't always stay on. Relating to the scanner, I bought it at the time of my post and it already paid itself off today. Last night it rained and I had my horn go off randomly like a few weeks ago. I discovered this morning that my SAM had been completely soaked by a leak. My scanner was able to show a bunch of shorts. I spent the entire day working on it then the real tailgate stopped working after I took everything out cleaned the SAM and reinstalled. I was able to clear the fault code and the tailgate functioned again.

Sirdoogles

Quick update, I scanned the Airmatic system and was surprised to see that the only code I got was '5400'- Check component F58kG (Air suspension compressor).

I decided to also take a look of the readings of the level sensors as well. Just looking at the values, my gut feeling is that these sensors are not calibrated properly. Vehicle was parked on a flat surface and did its self-leveling before measuring. Here are the values I got.

• Sensor Position: Volts / Vehicle Level (mm)
• Front Driver Sensor: 3.22V / -46mm
• Front Passenger Sensor: 2.06V / -42mm
• Rear Driver Sensor: 1.57V / -51mm
• Rear Passenger Sensor: 3.22V / -36mm

For the "Overall" Airmatic system voltage, I got 14.2 volts. To me, the values from the sensors looks off, but if anyone has insight on what the values should be, let me know.
As always, appreciate for the help.

Maj. Dundee

Why don't you try replacing the relay.

Sirdoogles

Another update. A while back I called a indy merc shop about my issue and he stated that those compressors should run quickly. The issue of mine running at prolonged periods of time could point to a possible weak compressor. My replacement did come from China so it could be in the realm of possibility. Since then I got no leaks but the same intermittent compressor is still there. Ill post more updates for people who are looking at this thread if something happens.

esphil

it was suggested earlier to change the relay, have you done that? Changing a compressor with a new one keeping the bad relay wont change anything.

Irfan Hassan

Just one air ride sensor located close to right side rear air bag.I found mine had bolt loose so i tightened, test drive and since then working fine.No issues