W221 air suspension fault

[Mow221]

In the process of going through my s class (w221 s320 cdi) i have a recurring issue with the air suspension, in general it works fine, but the passion arises when it just drops off, not usually when left parked but when starting or driving, air suspension fault msg on dash, fault stored for suspension system too long to refill...
I have replaced compressor and relay, fuse was obviously damaged and had the wrong amp fitted, replaced with correct. Replaced breather pipe, checked for leaks from valve block connections etc, all seem ok, compressor with work fine when activated via diagnostics, when setting up heights and setting adaptions.
Reset heights and settings saved ok, erased fault code, all ok. And again when starting and running over a few days, no sign of compressor kicking in and car drops off when moving around, and fault returns for too long to refill air system....
Any ideas? Suspension module issues?? Maybe a faulty relay etc? Or are there other places to look for issues? Note compressor with work when activated via diagnostics...

 

[zipdip]

Well there must still be a leak ,as you have found most of the important stuff regarding the air suspension takes place at the front nearside,with the compressor and small tank it fills,plus the pipe that feeds the system,the reason you have the fault that it is taking too long to fill the tank is because there is a time limit built into the software I think it is 5 seconds,this normally occurs when the pump is worn out,but you have replaced it and so the message will still be displayed if you have a leak,this would only be from compressor to tank and you say you have found no leak if the leak was elsewhere then the fault message would be different,I would suggest that you find a good indy and get star on it there are a number of tests they can do.

 

[Mow221]

I'm going to go back over the line connected to the compressor, and recheck the fuse and relay, I'm unsure if the compressor is driven through the relay for setup via diagnostics?

 

[Mow221]

Ive gone through the system again, and unless i have network issues causing the suspension module to act up I think i may know whats happening and ive tried an experiment to test my theory...
As ive been playing around with the suspension settings quite a bit (bold me!!) Ive generall left the settings quite close to the tolerance limits, which may not be allowing for natural sag/drop when not in use and may the be going out of range to allow the system to raise enough on startup etc?

Settings work in that the LF and RF sensors work away from each other, one voltage raises with height other voltage lowers with height, and the raer is a single height although has adjustments for both bags... so i try even out the amount i raise evenly on each side as i fill or lower, and have started from a completely drained system. so at present, car sits a tad high, but readings are as follows, fr/l 147mm,2.58v...fr/r 148mm,2.38v...rear 138mm 2.8v.
Ill try it for a bit and see if my theory is correct??

 

[Mow221]

Update, still not working! went trough again, cant seem to find where the fault originates? possibly in the suspension module?
Is this something anyone else has had issue with?
car will sit at set height for weeks, didnt move when doing the engine work, but as soon as it drives it starts to lower slowly and not refill, only since i had to crank for a long time after fuel leak, battery level went low...

 

[Mow221]

Coilovers are looking more and more tempting!!!

 

[zipdip]

Get it to a indy with a star where abouts are you somebody will know a indy near you.

 

[Mow221]

Get it to a indy with a star where abouts are you somebody will know a indy near you.

I have a guy that has star but we're not able to move around at the moment, will have to wait.

 

[mbmb123]

Depending on the year, you'll have either 4 height sensors(1 per wheel), or 3 (2 at the front, 1 at the back)
Maybe 1 or more is returning misleading information when driving.

 

[Mow221]

I've played around a bit with readings and settings etc, checked connections on suspension module, checked for restrictions from the air feed with possible blocked or restricted filter, also reset the height settings but moved car and steering to allow settings adjust correctly and readings not go out alot after driving.... Haven't been out much to test