[jmatta]

Yep on the voltage regulator. Unless the alternator shaft has wobble, the usual suspect is the regulator. It's a common part used on VWs, Audi and Mercedes. Do a search and you'll find part numbers from Bosch; they are under $50 and fairly easy to install. I did mine several years back after the car came from winter storage...battery light went on and I got out the multimeter. Think the reading was only around 11 volts, when it should be at least 14.