My A/C compressor seized up a while ago, the ECON light came on and the air conditioner would not work. A local shop replaced the compressor, after extensively flushing all of the debris out of the system. The new compressor worked fine for about a month, and then seized up again.

I took it back to the same indy shop, which flushed out the system once more and replaced the compressor for the second time under warranty for free. However, this time, the compressor didn't even try to engage at all.

The shop tried replacing the HVAC control unit/computer, but this still did not work. All of the functions (heating, fan) seem to be working, and there is no ECON light this time, but the compressor apparently is not getting any power. The shop also checked the refrigerant pressure readings, which were appropriate. Oddly, the condenser fans do still come on when the A/C is switched on, but the compressor doesn't engage. There is no ECON light, or any indication that anything is wrong.

Does anybody have any suggestions on what this might be? Any sensors or anything like that? Or could it just be a short in the wiring somewhere?
I'm not sure what means they employed to "flush out the system," but perhaps they were overaggressive and screwed something up?

Any help would really be appreciated.

 

For the record, my car is a 2002 B6 Audi A4 3.0 v6 quattro.

 

Need to get a clear answer from the shop on what's going on. You say the compressor won't engage, but the pressures are good. If the compressor doesn't engage, there are no pressures to measure. also, what else did they replace when they did the compressor the first time? Condenser? Expansion valve? Dryer?

 

This occurred to me also, and I thought it a bit odd when the shop reported that pressures were OK despite having no compression in the system. Perhaps there is some amount of ambient refrigerant pressure they were reporting? Or maybe they were just checking if there was any refrigerant in the system at all? I don't know.

I don't know for sure, but I'm going back to the shop later today and I'll ask. I have a scary suspicion that they didn't change any of those things and just threw in a new compressor (which would explain the subsequent seize-up). This isn't exactly the most reputable shop. Even assuming this worst case scenario, wouldn't the brand new compressor still get power? What's different about this time is that the ECON light is not on - whenever the compressor wasn't working in the past, the ECON light would always be illuminated. Now, it's almost as if the car doesn't even know there's anything wrong with the compressor - the condenser fans come on and everything. The shop keeps insisting that it's an electrical problem, and they're making me leave the car so they can disassemble everything and diagnose it (I thought they could just hook a computer onto it and figure it out, but I guess not). At the risk of financial suicide, I'm strongly considering taking it to someone else who actually knows what they're doing.

 

I am not 100% sure, but I am pretty sure the ECON light only works if the system actually sees pressures. So, if the compressor is not engaging, the system just thinks the compressor is not spinning. I don't think it is that smart, which is sort of the answer to your second question about hooking a computer up to it and getting an answer.

I would challenge them if they say all they did was replace the compressor. If they baulk, I would seriously consider cutting my losses and finding a reputable shop. German car A/Cs tend to be more complicated than most cars and without some research (which I haven't done on the A4) can't always be treated like any other car. I ended up replacing the A/C on a 1999 Mercedes that after some research turned out to be a "simple" system. Replace meant all of the components I mentioned earlier. It has run for 4 years now and was about 1/3 the cost. But, you have to do the research and go in with that knowledge or take to a reputable VW / Audi shop.

 

So apparently the only thing the shop changed was the compressor, nothing else. I guess this explains why the second compressor failed? They claimed that they flushed the system with acetone (???) and that should have cleared any debris from the old compressor. Anyways, the compressor that's in there currently is brand new and should be working, but just isn't getting any power. The last thing they tried was putting in a new "high-pressure sensor," which didn't change anything either.

I guess I have no choice but to take it somewhere else. I'll have them look at it, fix the electrical issues, and change the expansion tubes, dryer, and condenser flush the system again just in case.

I appreciate all of your comments - thanks for your input!

 

levansula: after you took it to the other shop what did they do and is it fixed I am having a similar issue on my 2008 A6 3.2L