If the generator will "motor" (either direction) it will also charge. Try disconnecting both wires (armature and field) at the generator, and running the engine at idle. A DC voltmeter should be able to measure at least 0.5 volts between the armature terminal of the generator and ground at the housing. ("residual voltage"). If that is there, the next test will be to attach a jumper wire from the "field" terminal of the generator to ground at the generator housing. With the field grounded (still no wires attached) the armature voltage should rise dramatically- - - -maybe 20 volts or more as the speed is increased. If the generator passes these tests, it's good. I'm going to guess your problem is either in the wiring harness between the generator and the regulator, internal problems inside the regulator, or a bad ground between the regulator base and the generator housing.
Drop me a PM, and let's have a phone conversation. I can share more test procedures in a 15-minute phone call than with a novel's worth of typing.
Jerry
Well, I think the field is bad. With the truck running and voltmeter connected, I grounded the field and got exactly 0V....
