New allroad suspension compressor won't work

**4rings2turbos** · 02-12-2011 10:31 AM

I'm not certain my shop's diagnosis is right, they did not sound reassuring, so any help or personal experience would be appreciated.

Just had my local indie shop replace my burned out compressor and FL airspring on my 01 allroad, both from Arnott. Received a call, they put the new compressor in but "the wiring harness was burned out and we can't do anything about it". After some online searching I haven't found anything relating to the plug-in for the compressor, but I did find several places where the wiring harness ends for the level sensors went bad due to the conditions they live in i.e. heat cold corrosion and moisture. Perhaps this may be the issue at the compressor?

The condition that my allroad is in is the FL corner is slammed, the suspension light stays lit in dash and there is no response from any buttons and apparently the mechanic couldn't get the compressor to work.

I've been without my baby for a couple weeks now and I thought I would have her back in fully functioning condition and the shop they suggested I take it to is closed until Monday, I guess I'm just looking for more explaination, if this is common, or maybe that their diagnosis was incorrect.

Let me know if any more information would help

TIA

-Thaddeus

**A62TURBO** · 02-12-2011 10:37 AM

What do they mean by the harness is burned out?

**4rings2turbos** · 02-12-2011 10:49 AM

That's why I'm concerned, I went to allroadfaq and looked up the suspension self study that they have because I really don't see what they mean, And I couldn't get a good answer. They have a mechanic there that is well versed in allroads, and I trust them, but this just didn't add up. And I don't really know what to tell the next shop when I take it in.

He sort of alluded to the fact that the compressor was running hard while my airspring started to leak worse and worse, and the heat caused the damage.

**onyrmom** · 02-12-2011 06:19 PM

Originally Posted by 4rings2turbos

He sort of alluded to the fact that the compressor was running hard while my airspring started to leak worse and worse, and the heat caused the damage.

The "harness" for the allroad compressor consists of a heavy gauge "ground and hot" pair for the motor, a light-gauge pressure switch pair, and a black thermistor that looks like an additional ground connector that is bolted directly to the heat radiator at the top (bottom, when mounted) of the compressor piston housing.

It's possible that the compressor ran hot enough to damage the cabling, but unlikely, as the thermistor would have told the suspension computer to shut down the compressor until the heat radiated off. You get a suspension dummy light, and the level indicator light flashes without allowing you to change the ride height at all.

Considering that you have already replaced the compressor with a new one, it is likely that either the shop misunderstood the purpose of the thermistor and cut it off, or that you have an error with the level sensor LF as mentioned before.

You can:

A: buy a Vag-Com from Ross-Tech, read the suspension error codes and figure out where the fault is yourself
or
B: take the car to a shop that actually works on Audis and have them read the codes out for you

Either way, you want the specific error codes that the suspension computer is throwing. Otherwise, the possibility exists that the shop is blowing smoke up your ass, and doesn't want to admit they don't have a clue what they're doing.

The fact that you're replacing only a single front airspring shows that you either don't have the $$$ or don't care if the front suspension/steering is off because of the mismatched front airsprings. So, considering that you're stuck with an undriveable car until you get this resolved, I suggest:
1: Buy another front airspring for the RF so your suspension will be even
2: If the error code indicates the level sensor is bad, replace it. If that doesn't do the trick, take the car to an automotive electrical shop and have them splice in new wires to the ECU. This should not break the bank.
3: If the errors show problems with the compressor, have the same electrical shop replace the lines to the compressor, as well as the temp-sensing thermistor. This also should not break the bank.

The labor to get at the compressor is ridiculously easy...if you have a lift. You remove three nuts that hold on a debris shield, and then three more nuts to remove the compressor itself. Read my build thread if you wish to see pictures of what it looks like. Personally, I replaced the entire wire harness from the compressor back to where the harness enters the chassis, as I installed the MBZ version of the compressor, rather than the Arnott spare. I should have done the Arnott, in retrospect.

Otherwise, I know guys in Calumet City that'll take that car off your hands reeeeal smooth-like.

**4rings2turbos** · 02-12-2011 06:51 PM

That is VERY useful information. I agree that I should get the exact code first thing.

I also didn't know that replacing only one airspring had any adverse effect, I was under the impression that it made no difference. I don't exactly want to throw my money away, but I definitely care about keeping the car in top condition, it's the reason I have Audi's. Despite them potentially being a lot of money (this one especially), so apologize to your boys in Calumet City, the only way anyone is getting the keys to this allroad is when I have the keys to another one ;)

I saw how easy it was to throw in the new compressor, the only reason I didn't do it myself was because it was in the shop anyway.

I truly appreciate your knowledge and advice. I just ordered a spring for my RF, and on monday I'll take it in to get the exact code and go from there.

Out of curiosity, who is it that you know in Calumet City? Knowledgeable Audi guys? Always good to network within the community.

**onyrmom** · 02-13-2011 12:24 PM

Heh, no Audi guys, just my mom's half of the family ;-)

**4rings2turbos** · 02-17-2011 11:50 AM

So, essentially it was the worst case scenario, the code was for a burned out control module. The shop bypassed the module and tested the pump and all other wiring and springs and everything works. So my options are to buy a new module from Audi ($840), buy the only used one on Ebay right now ($400) or see if I can find someone that will work on mine. The mechanic told me that none of his trans computer shops will work on it, and he's not 100% sure if he would be able to recode the used one from Ebay to my car- anyone have any experience with that?

**slick50** · 02-17-2011 06:42 PM

I would think the module should be plug and play no coding needed, module replacement is rare so just make sure they are willing to stand behind their diagnosis.