1989 Ford Ranger: alternator wiring harness - ASAP Jun 24, 2011How should the alternator be wired in a 1989 Ford Ranger. The one wiring harness has a thin ground wire and 2 large (4 guage?) wires. There is no indication which of the two large harness wires should be connected to the positive feed and which to the negative." Ford Ranger Wiring Diagrams : The Ranger Station Ford Ranger Wiring Diagrams . DISCLAIMER: Activities and vehicle modifications appearing or described at The Ranger Station and it’s pages may be potentially dangerous do not endorse any such activity for others or recommend it to any particular person – we simply describe the experiences and opinions of other Ranger/Bronco II owners.