I've got a 99 A6 quattro. While I believe my problem to be the battery, I'd like to rule out my alternator as the source of the problem. If I do have to replace the alternator, where can I find out what size (90 or 120 amp) without physically taking it out of the car. I asked my dealer if the vin number would be sufficient for ID and he said "no" that I would have to read the nameplate on the alternator. Thanks in advance for any input.