filip_a

So, I have had trouble with my airmatic system for a while now and need some more ideas what to do.

I got the "malfunction" message during driving. It went away after a while but then came back again. I noticed that the rear right would sit lower than the rest of the car.

Finally I inspected the compressor and valve block. I found that the intake hose to the compressor had many cracks, so I cut off the cracked part and put it back. I also replaced the filter. I later replaced the valve block.

But problem remained and the compressor was more noisy now (been using the car for a month or so). So I decided to replace the compressor.

Put in a new Arnott compressor yesterday and it is running smooth, but the rear wont lift. My icarsoft scanner tells me that rear right height is much lower than the rest. It sits at -82mm and the rest is more in the same region. I also got a code about airmatic pressure relief valve?? If I raise the car with the button, it will raise, but will not drop if I tell it to lower (from the dashboard button). Where is this pressure relief valve? I mean the compressor is brand new and also the valve block.

...So, I decided to check the level arm on the rear right, it was really stuck and would not move. So I greased it up and it is now able to move. But after I did this, the diagnostic tool tells me that the level for rear right is now 120mm.

I also found that after playing with the connector to the sensor which sits close to the rear right bag, the voltage on the diagnostic tool shows a different value. It is now 0.25Volts, the front has a value of 2.5-3.0 volts or similar, I dont remember the exact value now. And Rear left gives similar low output voltage now. Are these voltages controlled together?

Questions:

1. If the rear right sits low, will the airmatic raise the rear left or will both be sagging?

2. Should I check the wiring and connector for the rear right sensor?

3. Can anyone recommend a STAR diagnostic system which can be bought from Aliexpress or similar?

Any ideas are welcome.

Many Thanks

Max Blast

At any point did you check the rear right airbag for leaks?

When was the last time any of these airbags were replaced with new ones?

filip_a

The rear bags have been replaced 10mo ago by the previous owner. I have not yet checked with soap, but my guess is that the rear bags are fine.

I will check the valve block connections once more and also check the level sensor arms in the rear since the diagnostic tool is telling me that the sensor voltage for the rear is close to 0V. Not sure if it gives that value completely depending on what position the level arm is in??

Max Blast

Don’t rely on the voltages for now. And sure that you have four hole-free bags by raising the car, and checking with soapy wooder, stoner spit or leak detection spray.

The voltages will adapt to whatever the current calibration of the suspension is, the best you could ever tell that a sensor is working properly is that the voltages move around as you rock the car with your scanner tool plugged in. Your primary means of troubleshooting this problem should be visual an aural at this time, Put the scan tool down and go find the leaks.

It wouldn’t be outside the realm of possibility that a 10 month old cheap Chinese bag has developed a leak. Which would in turn have burned out your compressor from trying to fill it, which gives you the malfunction that brought all of this about.

filip_a

So, I suspect the rear right bag is leaking. After replacing the compressor and checking valve block air lines just to verify there is no leak there I still get the same error message.

Most likely the compressor burned out due to the rear bag leaking.

I will replace it and get back with results

Miguk_Saram

My 2 cents:

Disconnect the air line to the sagging bag, start the engine (or try to raise the vehicle) and see if there is air coming out of that line. If air comes out, then you either have a bad air bag, or a fracture/leak somewhere in the line that is keeping the pressure from building up.

If air does NOT come out, then, while the line is disconnected, play around with the sensor arm. Try angling the arm downward and see if air starts coming out through the disconnected line (you may have to open a door to trigger the airmatic). If it does not, then your valve block or sensor are the problem.

To test if it is the sensor, try swapping it with a known good sensor. If air still does not come out of the disconnected hose (with the alternate sensor), then your valve block is the problem. This could be something as simple as a valve stuck in the closed position (rust) due to moisture accumulation while air bypassed the intake filter through cracks in the hose, or the hose being disconnected. (what a horrible sentence that was!)

One last bit: the Pressure Relief (release?) Valve is part of the compressor. It's that second electric connection on the compressor itself (if memory serves).

EDIT:
Caution: you will be working UNDER your vehicle, so be sure to lift and support it adequately. You will need sufficient clearance below the vehicle to allow for the height settling all the way down to just the shocks (6" to 8" off the ground). For your own safety, do NOT work/rely on the vehicle being raised to get under it without adequate support (jack stands).

Max Blast

DO NOT do this unless the back end is on jackstands - disconnecting the line from the bag, or the line from the valve block will collapse the bag.

Miguk_Saram

Thanks. Max Blast.

I forgot to include my standard disclosure:

Caution: you will be working UNDER your vehicle, so be sure to lift and support it adequately. You will need sufficient clearance below the vehicle to allow for the height settling all the way down to just the shocks (6" to 8" off the ground). For your own safety, do NOT work/rely on the vehicle being raised to get under it without adequate support (jack stands).

Post editted... for redundancy.

filip_a

The valve block is brand new and I checked all the air lines connected to the block and they are all good.
The compressor is also brand new Arnott one, so impossible that there is a problem with the compressor.

I will do the test of the rear bag and of course will lift it up and put jack stands etc.

I anyway ordered a new arnott rear bag to keep, in case I need to replace on the bags in the rear =)

filip_a

Also, out of curiosity:

The electrical connector on the compressor that controls the relief valve, does anyone know what voltage should be on that connector and when is it applied? If I turn off the car, the relief valve should open and give +12 or +24V to a solenoid valve to open the pressure relief valve I suppose?

Max Blast

Two known good bags should be in the back; otherwise you’ll be chasing a leak in the other one shortly.

filip_a

So, a little update. The rear air bag does not leak, It will keep the same level for many days without dropping.

But, still, I decided to replace it just to be sure I have a good bag in the rear.

During the bag replacement I noticed oil leaking from the shock so I had to replace the shock to a new one too.

After replacing the bag + shock, the car is still sitting lower than rear left! I have also cleaned the plastic lever arms on all corners (they were sticky). After cleaning, they can move freely.

However, If I use the raise button to raise the vehicle, it will raise. But when pushing the lowering button, it will not lower and stays at the same height. If I turn off the car, it will open the pressure relief valve and set the correct height.

So, I am still not 100% sure about this airmatic system functioning properly.

I will also replace the rear left shock later today, since they look like original shocks and the car has now 190k miles on it. Since I am planning on keeping it as my daily driver, I want to be sure the airmatic is working well.

From my scanner after replacement:

Left front vehicle level: -36mn
Right front vehicle level: -29mm

Left rear vehicle level: -20mm
Right rear vehicle level: -46mm




Parts that have been replaced so far:
Rear shocks
Rear right airmatic bag
New arnott compressor
New valve block

Max Blast

You missed the left rear bag.
should also be replaced.
for reasons explained above.

then you can find a flat surface and run an auto calibration if your scanner can do that.
otherwise pull the battery and let the car relevel itself on that flat surface when you reconnect power.

filip_a

Yeah I know, will replace left rear later on since its not leaking for now.

My scanner does not have any calibration tools. Thanks for the advice, I will reset it by disconnecting the battery!

Max Blast

That left rear bag is going to blow as soon as it it most inconvenient for you.

filip_a

So just to give an update:

Car will still give the "malfunction" message sometimes. I suspect the chinese valve block is one culprit in this, so I will switch back to the OEM valve block and see if that changes the problem.

Also, if I push the raise button, I cannot lower the car once its been raised.