2008 A6 Allroad suspension gave up
 

Hi all,

Sorry for starting another thread on this issue, but I feel the journey will take a while and several major steps to fix over some time.

I have the car since new. I have driven 270k km on it and approximately a year ago, I started having issues with suspension. Some would say I should have sold the car, but I like it a lot and would like drive it as long as it remains in a piece :).

At first, it would go lower the rear of the car overnight when it was cold (like -20). Since it would rise quickly when started, I decided to wait with fixing it until it was not so cold. When it became warm, it was not a problem anymore and I forgot about it. At some point the car started doing this even in warm weather. Then it started doing this after a few hours. Then it started lowering the entire car. But it would always rise to normal level and be happy once started.

Now it has deteriorated to the point where it would not lift at all. I mean the car is so low that the wheels are inside the arcs and the ride (the little I have driven) is like there is zero suspension. None at all. Lifting the car with a jack is a funny business because if you are lifting front right, left right would lift, too. Time to do something about the problem I thought. I have connected VCDS thingy to the car, so I can see what the car is complaining about. I have the exact codes on another computer, but we have "implausible signal from level sensor", we have "unable to obtain initial position" or something that sounds like that, we have "compressor over temperature", we have some sort of "ABS failure" and some sort of "steering angle sensor problem".

Since the compressor does not run at all, I suspected everything related to if first. I checked the fuse - fine. I have the relay taken apart - contacts are kind of worn, but it does work. If it is long term good for 40A, I'm not sure, will change it, but its not like it can prevent the motor from running at all. I took off the compressor and tested it with another battery - works, sounds normal and puts out a lot of pressure. Tomorrow, I will do some testing of the temperature sensor of the compressor. The wiring diagram shows there is some sort of solenoid in the compressor. Any idea of the function of that thing?

What else can prevent the compressor from functioning at all? I cleared all DTCs, but still no joy.


Thank you for your time,

Edmunds

Since I cannot edit my posts, I will have to reply to the thread myself :).

Forgot to mention there was a time in between, when leaving the car in allroad setting would keep it "normal" at all times. Since this suited me moving to the countryside, I was not in a hurry to fix it as "allroad" setting was what I would have wanted most of the times anyway. Maybe this helps to diagnose one of the problems (which I'm sure there is a multitude of by now).

Edmunds

Hello,

I have exactly the same issue and have had it in my local garage without success, currently I have the car in my garage and I am checking various things. Is there a definitive drawing of where the compressor is located on a 2008 All road? All the ones I have looked at resembles nothing like mine, namely, in front of the spare wheel well, can anyone help please?
Cheers
Bridoh13

Well, the compressor should be easy to find - lift the car or at least the right front corner and look just in front of the wheel from underneath. There are three nuts to undo and you have the compressor. Practically, you will have to remove the wheel and the arch lining to access all the connectors and valve module.

Edmunds

Thanks for the info, have raised the rear, removed the the arch linings etc, I won't go on, I will attack the front this afternoon and let you know as soon as I have got somewhere.
Cheers
Bridoh

In my C5 allroad, if the compressor shuts down due high temp several times I must erase fault codes only then the compressor run again

An update.

I have replaced the relay - as expected, this did not fix anything, I still have absolutely no signs of life on the compressor. I.e. the control box refuses to run the relay, so that it enables the compressor. I have received a used but said to be working control unit - replaced, coded it the same as the old unit, nothing changed. I'm now waiting for a replacement comfort module as my best guess for now is a problem there.

I have since long had problems with rear lid - I have the automatic option, but the comfort module refuses to register the lid is closed. I have tested the microswitches, I have tested the wiring - seems to be in good shape. However, I still got the 'shotgun' effect when I close the lid, as the pulling mechanism is ratcheting nowhere for some 5 seconds with the lid as closed as possible.

The wiring diagrams I have, show a little green wire going from comfort module to suspension module. Needless to say, I have no description of what the signal is. I can only guess from VCDS description saying 'doors have to be closed, otherwise system will not function' that there is a 'door open' signal that is passed to the suspension module. If that signal is just a high/low or some serial message, I have no idea. If anyone knows, please shed some light. It may be, just may be, that if that signal is somehow erroneous, the suspension module goes on strike.

Will keep this place posted. Thank you for your attention,

Edmunds

Hi Edmunds, I know it's been a while but did the replacement comfort module fix the suspension problem?