What year and what engine?
Autozone has some good schematics. Try Figure 10 - Diagram 9
http://www.autozone.com/servlet/UiBroker?ForwardPage=/az/cds/en_us/0900823d/80/1e/b3/2d/0900823d801eb32d.jsp
Grey to ground, big Red to Megafuse, Green/Black to instrument cluster (battery charge light), and the small Red wire is supposed to be cut and spliced on the big red connector at the alternator (look at the diagram posted by Goldentour).
