Bad Alternator ? 2004 TDI BEW

[natem600]

While driving to work all the trouble lights on my dash light up and suddenly go out,along with the radio. The car was still running fine. I shrug it off as a weird bug, but then I accelerate from a stop and all the dash trouble lights come back on and the radio shuts off, the power windows and moon roof refuse to work but the car still runs. When I Tap the brake the radio turned on and the trouble lights go out and the windows / moon roof work. I noticed that as long as I keep the RPM's under 1200 everything is fine but @ 2000 RPM and up everything goes nuts. Tested the Alternator and its putting out 18.8 Volts @ 2500 RPM.

Second question

Why would high voltage cause the windows and moon roof not to work ?

Last question

How do I tell if the alternator has a Internal Regulator or is computer controlled ?

Thanks, Nate