moedip & Mike,
All right, I'll quit being lazy and remove the alternator. I had shown the black thing to a friend of mine last week, and he thought it might be some sort of noise (electrical) suppressor. The pigtail is too short to go much farther than the middle of the alternator. There is a gap near the voltage regulator it looks like it might fit into, but I'd guess not judging from the length and "memory" of the wire. I'll post againwhen I get it done. Thanks again.
'02 C230 Kompressor
'89 560 SEL "Frau BlueCar" (retired April 2004)