I have a 2003 A6 3.0 Quattro. It has 60K miles. I live in Michigan. Recently I have noticed a groaning sound whenever the engine speed hit around 1500 rpm. I took it to a dealer since I bought the car Certified Pre-Owned and it still has a warranty. The noise is very obvious and definitely corresponds with the AC compressor engagement. So when I turn on the AC the groaning starts and when I turn off the AC it stops. The dealer immediately suspected the AC compressor and replaced it. That did not solve the problem. At this same time I noticed that the charge indicator tell tale (the battery icon) lit every morning when I started the car and the voltage meter would read around 12V. If I revved the engine a bit, I could hear a relay click, and then the light would go out and the meter would read the appropriate 14V. So the dealer replaced the alternator. I still have both problems. Now the dealer says they can't replace the power steering pump (the only other load on the sepentine belt except for the water pump) because they would only be guessing and Audi doesn't allow that. So does anyone know what can be causing this annoying groaning sound? I think it is the power steering pump. Of course, I still don't know what is causing the low voltage situation at cold start up.