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To do that motor test, you MUST have the frame of the generator grounded at all times! With the field post ALSO grounded the generator should run as a motor and be surprisingly slow! If you remove the ground from the field post (frame still grounded) it should speed up. Re ground the field post with the frame still grounded and it should slow back down. Take careful note of the speed it runs. When running with the frame and field post both grounded it ought to run quite slowly. It will have pretty good torque too. In either case, if it runs real fast like it's a starter motor, you have a problem in the generator. If it runs but has dead spots and will only start to run if you first give it a spin, you have a problem in the generator. For the motoring test, the frame of the generator must always be grounded unless you're working on a 24 volter off of a JD. They're different aminals! One thing nobody mentioned is that the regulator cannot operate or control the generator if it has lost its connection to ground. One more item I'd suggest.... Try the motor test with the generator still attached to the engine. Remove the drive belt. Remove the field wire from the field post of the generator or regulator. Jumper from the BAT term of the regulator to the GEN term of the regulator. The generator should begin to motor. If it does NOT motor like this, jumper from the battery's non grounded post to the ARM terminal of the generator. If it now motors, you have a harness or connection problem someplace. If it still doesn't motor, leave it connected and then jumper from the frame of the generator to the battery ground post. If it motors this way but not without this ground wire, remove and clean all of the generator mounting brackets, bolts, mount flanges and ears. I have seen corrosion float the generator bracket above ground & cause the persistent charging system failures you describe. When the generator is motoring (by the connections above) ground the field post. If the generator is good it will slow down and continue to run but slowly. If it doesn't change speed when the FLD terminal is grounded, you have a bad generator. If it DOES change speeds, you probably have a harness, regulator, regulator ground or some other connection problem someplace. Using a volt meter to test voltages can sometimes give you a false good feeling. You can measure full voltage at a post but still not have current carrying capacity that is worth a hoot. Motoring the generator USING THE TRACTOR'S WIRING HARNESS tests the whole shootin match! Good luck and post back with your findings.
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