Wiring diagrams are in most old Shop Manuals which it sounds like you should get. Some in store here on this site or at vendors listed in Links. I'm thinking there is also a link to a site that has the wire diagram for about your year truck. Check the links first. Without the diagram and following the wires around to all the devices, pretty hard to help you over web. I would say a wire from your alt is hooked up wrong and giving you a "draw" on battery. The light on dash for gen makes me think that. There is a wire from key switch to gen or alt to start it charging, maybe that's not there or right. We're just guessing here with out seeing or more info. Libraries have lots of books and manuals if you ever visit them. If it's a reference book you can't take out, you can take copies of it for small fee sometimes. My library has big books of wire diagrams themselves, just don't go older than 78 or so. Maybe if yours is bigger place, they will have more. Lot's of Chilton's and Motor's books there too, I'ld bet.
