Could it be the alternator?
 

The car is 2002 A6 3.0 w/85,000 miles and added information is the timing belt was replaced 10,000 miles ago.

Problem I'm having is this:

A while back my car battery light(red one) would stay on after I started the car and my voltage display would show it around 8 volts. If I reved the engine a bit the battery light would go off and the volt display would go to 12-13 volts and the car would drive normally. I figured the voltage regulator was going out and as I understand it the voltage regulator in these cars is contained inside the alternator.

Then tonight my wife was heading home (about 40 miles) and at about 7 miles from home the battery light(yellow) comes on and the voltage display slowly starts dropping. As she pulled into the garage the car died as she was closing the power windows.

I went out and tried to turn the car over and though it had a little power as I turned it over the juice was sucked out of it before it would start.

I then got the jumper cables on our other car and jumped the A6 off and it started right up. However the battery light(red) stayed on and the voltage never went higher than 8 volts and slowely died even if I reved the engine.

Alternator going out a slow death?

Mine had similar issues about a month ago (02, 2.7T). Replaced the alternator and haven't had an issue since.

Your problem is either the alternator or the battery. Based on your description of the symptoms I'm leaning toward alternator. Any reputable shop, and most of the chain auto parts stores, will test your electrical system for free and let you know which it is.

That alternator is toast.. i would suggest having yours rbuilt as you know what you have ..

Weak alternators kill batteries so you may need another one of those too now but since the weather is not to bad it may nbe fine. put the battery on a nice slow charge and let it build up while your getting your alternator rebuilt.

On our 2.8 we needed a new voltage regulator/brush pack about 8 months ago. For the 2.8, you don't need to remove the alternator to change out the volt/brush.. just flexible arms. I think we paid about 80-90 dollars for the part.

I was under the impression that the voltage regulator was all part of the alternator assembly, no?

Yes it is . I think what jeff is saying you can get to the alternator and change it while still on the car .. mind you he must be Mr. Fantstic is disguise.. :)

What should I expect to pay an independent shop to replace an alternator? More than $400?

No, what I said was correct. On the 2.8(and pretty much any euro car), the voltage regulator and brush pack are 1 removable assembly.

This is an EXAMPLE, not the actual part you need. http://www.carpartsdiscount.com/auto...tml?3593=57777

Changing it just means popping the back cover off the alternator and swapping out the part. NOW, you need flexible hands to get this done on the 2.8 as it's a tight fit.

Below is just a random pic I found of what the back of your alternator sortof looks like. The pic is with the back dust cover off, and right there is the regulator, held in with jut 2 screws. Unscrew, pull out, put in, screw and your done. Now only if it was that easy. It is with the alternator out of the car, but with the 1in of room you have in your audi, those flexible hands come in handy.


***it's possible the 3.0's alternator does not have a removable voltage regulator, but I highly doubt it. If so it's reason 10123 to avoid the 3.0***

http://www.davebarton.com/AdjVR-015.JPG

It turned out to be the alternator, had it rebuilt for $150.

Looks like my battery is shot now though. The battery is at least 5 years old.

Just adding a little info here, when the battery is below 10 volts and the battery is jumped and the car run, this often destroys the alternator by overheating it..alternators are not made for continuous duty cycle ...... a bad battery can kill them quick. I change batteries out at the first suspicion of slow starting or other symptoms of low power. batteries are cheap, alternators are expensive. I have never had a reconditioned alternator that lasted longer than a year...I just buy a new one.