Charging system gremlin

These are an incredibly simple system. The VR MUST be grounded. The IGN terminal of the VR receives 12V from the "run" circuit, and does two jobs--it powers the VR/ field circuit, and also is the voltage sense. The VR when the battery is low, sends field power on green to the flag terminal on the alternator, and the more current, the higher the alternator output. I would check that you have continuity from the one flag terminal of the alternator to ground. If it will not charge, rig a voltmeter on the battery, and with the engine running "fast idle" take a jumper wire, disconnect the green wire at the alternator , and jumper 12V to the alternator field terminal. This should cause full output.

If that works, but it won't charge with the VR and wiring all connected, it might be something in the wiring, or might just be bad VR. To be sure, disconnect the VR wiring, and jumper the two wires temporarily together. Start and run and it should charge, actually overcharge. If that works, and you are certain the VR has a good ground, replace the VR

You can easily burn up a VR by a field short to ground, so use reasonable care