Bosch Alternator: # 0 120 468 004, 005, 006 depending on MY > N --> 14V 40/115A
Porsche: #928 603 011 05
Bosch regulator: # 1197311021
Porsche: #928 603 142 00
Several parts belonging to this alternator (006) are available on this PDF on a Brazilian Bosch Website...
PS: you can possibly "Re-Set" by disconnecting the battery. This will only apply when you have a healthy one. Any bad batteries can be responsible for strange and erratic behavior of the alternator.
Here's an interesting link for a rebuild procedure
Jus found an old email from A German 928 owner. He has an 89 and says the
pulley has been changed from engine number M82.42 onwards.
Here are the bearings he put into the alternator of his 89 (purchased through BOSCH):
(NSK) 6201DUS 208 CG14B
(NACHI) 6303NSE2 F3 60 C/14 LI
The alternator originally had the following:
(NTN) 6201LUA CS20
(FAG) 565233 S 176
He paid about $20 for both bearings. He did not write anything about brushes or the regulator.
When I was in Germany last time I got a ride in his S4 with new bearings in all moving parts on the front of the engine. Despite lots of kms on the odo, this engine sounded as smooth as the 23,400 km GTS that was there also.
Additional information on repairing a Bosch alternator: Alternator & Regulator - Bosch.pdf