aTOMic

So I am reveling in the glory of my Bentley manual (which I bought a while back but have just had time to browse) and the car decides this is a good day to go flat. Twice before it happened and I ran the Auto-scan and cleared codes and all was fine for a while. This time no such luck. After exhaustive and frustrating searching on here, I have some questions that I can't seem to find the answers to.

1) Are all the air suspension fuses (big and small) in the panel near the compressor relay?

2) I saw some references to ability to read the actual pressures in the system; how does one do this? Does this actually help to determine the area of leakage?

3) If the compressor is about to croak, can it cause the DTC for air leak? (I hope)

4) Do the level-sensor arms pop off somehow when the car is riding flat? I saw one post where the poster claimed that could happen, but did anyone actually have it occur?

5) Where is the current cheapest place to buy a compressor? I am especially interested in the scheme of buying the mercedes-spec WABCO unit from Arnott and swapping plugs to adapt it to Audi. Does this work on our cars or is it Allroad-specific. (the MB spec unit is several hundred cheaper than the Audi one).

6) Any chance the compressor relay could cause all this mayhem? (Yes, I am an incurable optimist)

I'll post the VCDS scan asap, it says air leak, compressor overtemp, lower level exceeded. IIRC


The compressor runs but is slightly noisier than usual, I think. If I try to set the suspension via MMI it goes back to "automatic" after three seconds. Both suspension lights are blinking in the cluster. The back of the car seems not to be all the way down but pretty close.

I wonder if anyone has ever plumbed an air valve into the system for emergency use. Seems easily accomplished and would be safer than riding on the bumpstops.

Thanks in advance for input!
-Tom

MP4.2+6.0

He seems to know the system well, did the WABCO change (pre-Arnott era AFAIK) and for a lot fewer $, etc.

I have had no issues w/ mine, but have gotten the take away that if it is "going flat" to figure it out pronto and not keep driving. The recurring theme seems to be it may often be a physical leak in the system somewhere (like at an air strut), but if uncorrected it over works the compressor and then that is expensive toast too.

mishar

1) As far as I can see in ELSA there is only one and it is close to the relay.

2) It probably would help but it can also prove to be quite complicated. I wouldn't go that way.

3) I don’t think so. Just overheating.

4) No with OEM links. May be with shortened ones.

5) No clue here and I hope it will stay that way.

6) No. It will be burned by extensive current drawn by a dying compressor.

Introducing an emergency valve is very good idea. Close to the reservoir probably.

Since that both ends are down I would check valve block besides compressor.

aTOMic

Thanks, Misha and MP, my search is not working and it's driving me nuts!

My compressor is not any louder than normal, I think I was wrong. I still think it's on the way out because of the "implausible temp sensor" DTC. I think I had a "high temp shutoff" DTC a while back but I realize this could be from overwork caused by a leak or valve block malfunction.

there's a TSB on replacing the relay with nice color pictures of burned (big) contacts, it advised taking apart the relay to check... mine appears new except for the small contacts which look like old points, hoping replacing it solves the prob (I ordered one a while back).

Going out to reassemble now...

Mister Bally

I drove over 300 miles in the winter with no air(bad strut, compressor overheated, auto shut down) rough ride but no real damage.

Noisy compressor usually indicates the #1 WABCO electric compressor failure mode: a magnet came unglued in the motor. You can disassemble and JB Weld it.

aTOMic

Boy, I bet that trip was no fun. I hate driving it "flat" at all because of the hobby-horsing, and the streets are very smooth around here.

The noisiest it's ever been does not sound much like a loose magnet, just like an aquarium pump. What concerns me is it is louder at some times than others. These cars are so much like humans, i.e. any changes can be significant. I have named my car "Audrey". I am not crazy, she is.

mishar

If your compressor sounds fine it may have been overheated just because of leak prolonged work. Check the valve block since both ends went down.

MP4.2+6.0

In the last year or two, increasingly I find problems w/ AW search. Sometimes just doesn't seem to work, or returns no hits when I know from experience there should be a lot. When need be, I just use the Advanced Search feature of Google and point it specifically at the AW domain. I can't necessarily narrow it to the D3 board (or don't know how to...), but if I just put A8 or D3 in as part of the words to search on, it usually gets me to the right results.

aTOMic

Thanks, MP, I'll do that...

Sorry I don't have VCDS to post, but how do I check the valve block, beyond remove wheel & fender liner, and get a look at the thing? VCDS I assume??

After hooking battery back up and starting car, all four suspension choices are lit normally on MMI, the compressor runs for about 60 seconds and then it shuts off and only "standard" and "automatic" remain, the others are greyed out. The car stays slammed in the front, but I think the back is just reeeal low, not flat. I could be wrong, though.

aTOMic

I think when the compressor goes I'll just replace it with a liquid CO2 tank, then it'll be silent and I'll have an onboard flame suppression system too. Added advantage is the fact that no moisture could be introduced to the system due to the nature of liquid CO2. I am only halfway kidding. I already have virtually all the components, just need to see if any of my old buddies still work at the welding supply place to get my tank filled free!