ADS Problem

[v12man]

I have a 1990 500sl the suspension has lowered and gone very stiff, it wont
react to the ride height switch or the damper setting switch, I have bled the system as described and the car raises to full height, but when I reconnect
the valve arms it lowers again, the lights on the switches come on when pressed
but nothing happens, the warning light on the dash stays on, it would appear to be electrical, and the manual is very vague as to where everything is. my car has ads front and rear, the dealer near me said most only had it on rear, Help.

 

[television]

Hell V12 man and welcome. Your fault is not easy as you have found out.

I do know that the module has to be programmed to set the height front and rear to restore normal ride height.

We have a member called Stats 007 who knows these cars well,see what he thinks.

Malcolm

 

[Hibbo]

There was a link posted somewhere to an excellent description of how the system works and how to fault-find on it (albeit on a w140).

 

[television]

There was a link posted somewhere to an excellent description of how the system works and how to fault-find on it (albeit on a w140).

Both modules (red ledgend) have fault code read outs, on looking at the system it does need STAR to raise both ends to set to the ride height.

I don't think it can be done without STAR

Malcolm

 

[Hibbo]

http://v12uberalles.com/Adaptive_Damping_System.htm

Have a read of this, I'm guessing it's a similar system to that of your SL. Good reading, hopefully it may help a bit.

 

[television]

That guy Hibbo knows what he is doing. back in those days the diagrams were in the printed form,and were nice as you can see what everything does.

The Data now is horrible with no real info. I sent off for a paper back diagram service book last year for the whole series,but my $28 was lost as the book never came.

With the electronic data now supplied to cars,if this was the same for TVs I would have stopped years ago.

Malcolm

 

[stats007]

To be honest ADS is a nightmare and I'd leave it to a garage. The ADS 2 system has a number of changes but works on the same principle. It does sound like the diaphragms in the pressure spheres could have failed - although if the fault light is on it means an electrical fault is present (can be read out) and the system defaults to emergency operation and sets itself to the firmest damping setting.

The dealer referring to ADS being at the rear probably means that there are only two spheres at the rear for the system - the front dampers have a valve system to switch between volumes of fluid flow.

 

[gfern]

Sorry to hear about your problem, there is very little info on any of the forums on this topic as it is generally not a DIY fix, unless it is just the spheres or leaking pipes and valves which can be readily seen. Just a point my 1990 car has four spheres one in each corner, they are easy enough to replace as are other components the problem is knowing what to replace. I really think that the sensible option is to find a mechanic or garage that has some experience with the system and let them do it. From your description of the fault it doesn't sound like it is the spheres.
Best of luck.

 

[eric242340]

Your problem is the rear pressure bowls. spheres as some folks call them. There is a risk that the rear struts have a problem, but 90 percent are the the pressure bowls.

 

[Hibbo]

I know from SLS that failed accumulators (spheres) will give a very hard ride, but they won't affect the ride height.

It sounds like an electrical/control problem. Find a specialist who has a good working knowledge of the system, you may have to have a good search around, but there must be someone who knows it! (GLC maybe? )

 

[eric242340]

I know from SLS that failed accumulators (spheres) will give a very hard ride, but they won't affect the ride height.

It sounds like an electrical/control problem. Find a specialist who has a good working knowledge of the system, you may have to have a good search around, but there must be someone who knows it! (GLC maybe? )

Correct, they may make a kangaroo style ride, but they can only give a low ride height. so back to basics,

 

[eric242340]

Correct, they may make a kangaroo style ride, but they can only give a low ride height. so back to basics,

Now im confused, if the pressure bowls fail the struts can accept full pressure, also giving a firm Kangaroo ride, and this would mean the ride height sensors are at full height. Therefore the sensors send the wrong signals and it could happen the opposite way the level too low, hence same bad signals Had not thought of it this way before, any opinions?

 

[v12man]

I dont think spheres are to blame, (my car has four) as it would still raise and lower, I think ? I can raise and lower car from underneath by activating distribution valves manually, does anyone know the name of the orignal diagnostic tool mercedes used in early ninteen ninty the diagnostic equipment I have can only read o,b,d type cars from 98 onwards, I have tried it but no joy
P.S Thanks everybody for your help.

 

[stats007]

You can read/clear any of the DTCs using an LED and the 38-pin diagnostic port.

 

[television]

I dont think spheres are to blame, (my car has four) as it would still raise and lower, I think ? I can raise and lower car from underneath by activating distribution valves manually, does anyone know the name of the orignal diagnostic tool mercedes used in early ninteen ninty the diagnostic equipment I have can only read o,b,d type cars from 98 onwards, I have tried it but no joy
P.S Thanks everybody for your help.

All I know is that when coupled up to a STAR test set, this has the ability to raise either end of the car or both, also if it works the same way as the roof, then if nothing in the memory it will not do anything. I did read that if the height limit or ride height is not stored it will not go anywhere as it does not know where to go to.

If a Star test set will not raise the car , then the fault codes can be read out on STAR or as stats says on the 38 pin socket.

Malcolm

 

[Hibbo]

Now im confused, if the pressure bowls fail the struts can accept full pressure, also giving a firm Kangaroo ride, and this would mean the ride height sensors are at full height. Therefore the sensors send the wrong signals and it could happen the opposite way the level too low, hence same bad signals Had not thought of it this way before, any opinions?

You are indeed confused my friend!

The ride height has nothing to do with the applied pressure or the serviceability of the accumulators. The pressure in the struts will always be the same no matter what the ride height or damping settings are. This is because the weight of the car is always on the struts. Knackered accumulators will not affect ride height, only damping.

The ride height is controlled by means of a closed loop feedback system. If the car is on the deck and you select it to high ride height (or whatever it's called) valve(s) open to send more pressurised oil to the strurs. The valves then shut off when the struts have reached the correct height, as determined by the ride height sensors (on the rear ARB on my w124's SLS). Ride height is NOT controlled by flowing a set quantity of oil NOR is it done my altering the working pressure.

The accumulators are required as hydraulic oil (as indeed any liquid) is incompressable (ible? ) therefore the struts have no damping effect - they are hydraulically locked. The accumulators contain half oil and half gas, when you go over a pump the oil is pushed out of the struts and into the accumulators COMPRESSING THE GAS, this is what gives them some 'give' and thus a damping effect.

The level of damping is governed by solenoids that restirict the flow of oil to the spheres - if these are closed it is harder for the oil to get to the accumulators therefore the 'give' offered by the compressable gas is reduced and the ride stiffened. (Think of the struts as being half hydraulically locked)

A knackered accumulator will result in its strut being hydraulically locked and thus giving a very hard ride. It will not affect ride height. (assuming there's enough oil in the reservoir - which there will be)

Phew, not bad for someone's who's flashest motor is a diesel estate!

I'm by no means an expert, this is just my interpretation of these type of systems, so please educate me.

PS. Sorry for sounding like a ponce using words like 'thus' and 'therefore' all the time!

 

[television]

Now im confused, if the pressure bowls fail the struts can accept full pressure, also giving a firm Kangaroo ride, and this would mean the ride height sensors are at full height. Therefore the sensors send the wrong signals and it could happen the opposite way the level too low, hence same bad signals Had not thought of it this way before, any opinions?

Eric as you have so many SL's with ADS faults in China, and all of the test equipment and knowledge as a Main MB service and training center, that's something we do not have in the UK. There are few MB dealers here that will try and fix these things through lack of knowledge and experience. You are so lucky having the knowledge of these things

Why don't you post the full testing and set up procedure, clearly you know so much about them it would be so useful to other members.

Thanks. Malcolm

 

[gfern]

Hibbo
You are forgiven the poncy words, thats about the best simple description of how it works I have read on this subject. However in practice its still a pain to diagnose when its not working properly.

 

[television]

Hibbo
You are forgiven the poncy words, thats about the best simple description of how it works I have read on this subject. However in practice its still a pain to diagnose when its not working properly.

What a super post by Hibbo , as eric has all of the info on his 2000 test set I look forward to him putting up the info we need to complete.

Malcolm

 

[Bolide]

Good explanation, Hibbo

While you're on a roll, what causes the rear end to rise up & float about with no damping?

If a knackered sphere gives no damping (no gas), what fault makes the rear end float about undamped?

Nick Froome
www.w124.co.uk