njroute22

Been trying to "fix" my air suspension in my 2004 A8L for the past year. Has not ridden right.

Long story short - replaced the following:
- All 4 struts
- air compressor
- valve solenoid block
- all new control arms across the board
- sway bar and links
- even new tires! (Vredestein Hypertrac - highly recommended)

The ride still stinks intermittently!

No leaks.

Sometimes it rides like a brand new car - and other times it's as stiff as rocks (every road imperfection felt.) There is no rhyme or reason as to when it happens. I'm not even sure what is causing the struts to "stiffen" up. I cannot determine if something is electronically stiffening the shock absorbers themselves - or if it has to do with the air springs.

I get no fault codes in 34 ride control.

I had one fault in 55 "headlight" connected to J197 (I recall 01310). I cleared it and the ride improved shortly and the fault never came back.

My question is - can the J197 Air Suspension Control unit go bad or work intermittently (i.e., make the ride horrible) without there being any faults? It's a cheap fix to do. My guess at this point is something is going awry with the shock absorber adjustment valves (N336, 337, 338, 339) which are controlled by the air suspension control unit.

I also wonder if it has anything to do with the J104 ESP Control Unit (lateral acceleration sender) or the J527 Steering column electronics control unit (steering angle sender)- as those also work in conjunction with J197 Suspension control unit.

Has anyone else had this issue where *sometimes* the ride quality is awesome - only to have it go down the tubes for no apparent (identifiable) reason? It's driving me mad.

njroute22

I should add (I was going to make another thread about this topic) that I hear the compressor relay switch on and off quite frequently during the ride. Is that normal?

Could the accumulator tank in the back have anything to do with this? Perhaps a leak there?

I thought that once the accumulator fills to 16 bar - that should be enough to adjust the struts as necessary without triggering the compressor. I will be checking that next week nonetheless.

Running out of options to check. Knowing my luck it's probably some totally unrelated issue causing this problem.

PS - I read somewhere one guy had all sorts of electrical problems that was caused simply by a bad HVAC blower unit. Weird how these Audi's were engineered.

quattropowerA8

The same thing happens to me, the compresor works too much for me, and I also thought of an accumulator leak, but after changing the valve box, everything remains the same, and no leak is detected. what we have detected, in channel 6 of vcds measurements, is that the pressure of the accumulator, looking at it while running, fluctuates a lot between 15 bar, and suddenly drops to 3 bar, so I begin to think of a control unit or a valve box wiring . You can do that check on channel 6, maybe it will happen to you like me and we will be able to find the problem

njroute22

Thanks. That information leads me to believe that it really is the J197 control unit causing the issues. Even if "intermittent."

My car sits level - no air leaks in the struts.

I still think it may be the accumulator to some degree because we also have the same fluctuation between 15 bar and 3 bar. Like it's all over the map. Why?

But the reason I don't think it's the air "springs" is that the actual levels are fine. No sagging whatsoever. I think it's some kind of electronic stiffening of the shock absorbers themselves that is being actuated by the control module.. for whatever reason.

(NOTE) - I can make the ride nice again by activating jack mode - then deactivating it... I did that tonight and the car rode nicely. I have to see if it will change over the next day or two.

Either way - I'm changing the control module nonetheless.

quattropowerA8

[QUOTE=njroute22;25720970]Gracias. Esa información me lleva a creer que realmente es la unidad de control J197 la que causa los problemas. Incluso si es "intermitente".

Mi auto está nivelado, no hay fugas de aire en los puntales.

Sigo pensando que puede ser el acumulador hasta cierto punto porque también tenemos la misma fluctuación entre 15 bar y 3 bar. Como si estuviera por todo el mapa. ¿Por qué?

Pero la razón por la que no creo que sean los "resortes" de aire es que los niveles reales están bien. Sin flacidez en absoluto. Creo que es algún tipo de refuerzo electrónico de los propios amortiguadores que está siendo activado por el módulo de control... por la razón que sea.

(NOTA)- Puedo volver a hacer que el viaje sea placentero activando el modo gato - y luego desactivándolo... Lo hice esta noche y el auto anduvo muy bien. Tengo que ver si cambiará durante el próximo día o dos.

De cualquier manera, voy a cambiar el módulo de control de todos modos.[/QUOTE
]When there is a fault, the control unit selects the most rigid mode for the hardness of the damping to ensure driving.
I have a document that may help you understand what your problem may be, but I need your email to send it to you.

aTOMic

Although it shouldn't affect ride quality, have you replaced your suspension compressor, OP? Any time the pump works too much I suspect that.

quattropowerA8

The compressor has been repaired 2 times, but when it works so much, it breaks again. I won't fix it again until I figure out what the real problem is. I think it must be either the control unit or the wiring, and I think it will be the wiring, something difficult to diagnose

njroute22

I sent you a PM. Thanks in advance!

MP4.2+6.0

Just as a wild *** guess/shot in dark, have you ever changed the compressor relay? It is not in the list of changed parts at start of thread, yet compressor is. Known wear item, and many go by 100-150K miles. Having dissected mine (2006) after changing it at maybe 120K miles with some weird compressor issues that showed on the MMI screen as only two of four suspension modes available, the relay contact points were definitely worn and pitted. Simple relay change cured issue in full. It was just a guess for me BTW, and I had even bought a compressor the prior week figuring that was likely it. But I did relay first since I had it on hand (more below...). There was no VCDS code pointing me to issue either, nor do I really remember posts saying relay comes up as a code by itself. It is just an old dumb relay with simple trigger signal and power in-out when you see it; no fancy control box type stuff. Somewhat painful to extract from under driver's dash, so some may just try to ignore it as long as possible and hope for best.

Theory applied to this post and set of descriptions might be if relay connection is poor, it could cause compressor to flutter off and on, or maybe stick in the powered/on position with contacts hanging up and eventually burning out compressor, plus maybe maintaining pressure erratically. IIRC, standard advice or even compressor warranty requirement is to replace compressor relay with any compressor change, Same thing should apply logically with any compressor rebuild or similar work. Current through this relay is relatively high given it has to switch that compressor off and on; might be highest consistent draw relay on car (starter relay is integral w/ starter on Audi's).

FWIW, the three not too pricy parts some folks who are breakdown savvy, worried or **** about that they carry or have on hand are compressor relay, brake light switch and engine crank sensor. Remainder like air shocks, trunk motor, sunroof air foil motor, tail lights and a few others are just too pricy and/or unpredictable.

njroute22

Yes - we did, sorry didn't mention that. However, we've had this same relay in for the past few months - during which the car was acting funny. So next week I will install another new relay just to cover my bases.

Update - I think I'm getting closer to solving this problem. At least that is my gut feeling.

At some point, the suspension was so messed up we could not get the system to calibrate. We "MacGyvered" one of the leveling arms to make it shorter so the VCDS would allow us to calibrate. My Audi guy said it didn't matter that one was shorter, just that we entered the proper measurements when calibrating.

However, now I'm beginning to think this is the source of the "stiffness."

As of now - the car rides nice. After setting it to jack mode then disabling it. The last two days of local driving it has been a pleasure.

I determined that the car gets "stiff" when in Automatic mode and driving at over 80MPH and the system lowers. When the system raises again after the highway speeds are when the problems begin. I think the J197 module is sending a message to the struts to stiffen up because the ONE level sensor we made shorter tells the module that it is TOO LOW. Just a gut feeling. I do not have the exact specs or understand the programming of that module, so it's just a guess.

So next week, I will fix that level sensor to make it the same as the other side. Then I will re-calibrate the heights in VCDS. I'm hoping that is the problem.

If that does not solve the issue - then we go on to the next step, which is to put a new J197 module in. Hopefully it doesn't come to that.

I'll update my findings then.