70 amp to 80 amp alternator on 89 300e

I'm going to change alternators per suggestions from the board.

can someone give spefic wiring instructions.

[mbdoc]

Of course the easiest way is get the 1990 alternator wiring harness # 124-543-45-26 for $56. Otherwise you must crimp connectors onto the old harness & then solder.

70 amp unit has a 3 wire plug.
80 amp unit has 2 studs and a rather internal
looking single plug. Dealer does not have harness. On 89 amp unit studs are marked + -
what is 3rd wire?
thanks