Original 1991 Chevrolet Dealer Electrical Wiring Diagram Service Manual. This very informative Factory Manual covers S-10 Pickup Models. These detailed Wiring Diagrams are what the Dealership used to diagnose and repair your Chevy. Good condition with normal wear and soiling from use in a Dealership [see photos]. Very useful and rare since they were not offered to the public. ST 369-91 EDD