D15 charging problem?

I have a D15 series I that has stopped charging. I had genny checked and VR checked a year ago.Put a new VR on it, the mounting rubber has already failed. My starter generator altenator man has retired. What would cause it to not chage? I added a ground wire to battery ground and it didn't help. I notice discharge on meter when cranking, but no charge after it starts. What is best way to isolate my problem?Who has a good American made VR for it? I am not an electrical guru. Thanks Tracy

cottonpatch wrote: Napa sells Echlin VR. Solved my charging problem on series II 15. It was pricey at close to $80.

I will try them. Meantime I need help on diagnosing problem. Thanks Tracy

Generators are easy to test Tracy. The first quick test I would do is run a jumper from the F terminal to ground and run the engine at half throttle and above. If it charges, investigate the F wire from the generator to the regulator.
From there pull the belt off the generator and disconnect the wire on the F terminal at the generator. Using a heavy wire run from the battery negative if it's positive ground or battery positive for a negative ground system to the A terminal on the generator. A set of jumper cables works well for this. The generator should spin fast like a motor. While motoring, ground the F terminal. The generator should slow down, but continue to motor. If the generator passes these tests without excessive arcing at the brushes, it's good and your problem is elsewhere.
Next step is test your wires. An ohm meter is not a good test method here because one tiny strand of wire will show very low resistance, however, that one strand of wire will not carry enough current to make the system work. My preferred test light is a headlight bulb. The bulb will pull about the same amperage as the field circuit does. Using a headlight bulb, make a simple circuit using each wire between the generator and regulator. Bright bulb = good wire. Do the same light test on the BATT terminal of the regulator. Bright bulb = good power supply to the regulator.
The regulator needs a good ground through it's mounts. If you look closely you'll see on of the mounts has a wire connecting the body of the regulator to the mounting bolt. Buff off any rust under the mount making sure you have a good electrical path back to the battery ground. Still doesn't work? Replace the regulator. B&B Steve knows where the best quality regulators are available from. You can shine up the points inside the regulator and get it working again, but that is typically a short term repair.