voltage bad on 1990 Chevrolet Corsica

had new altenator checked its good. was told it could be a bad wire? found 3 wires bare coming from starter. one coroded going into a black connector was wondering what would happen if i wired that direc, the connector looks like its just attaching wires together???? please let me know what you think Please

Asked by for the 1990 Chevrolet Corsica
Here's a online wiring diagram, Follow them closely or you can really damage your electrical wiring harness.