Over charging
Simplified circuit. Ignore the dotted lines marked "old"
Power comes in from top right, this is the blue "ignition run" from the key. Power goes to the VR and to one terminal of alternator field. The field is ONLY connected to the two brushes, it is a simple electromagnet. The "existing wire" at bottom going to the VR is the green. The VR controls grounding of the green to control output. You can replace that with a jumper to ground for testing. VR MUST be grounded.
Simplified circuit. Ignore the dotted lines marked "old"
Power comes in from top right, this is the blue "ignition run" from the key. Power goes to the VR and to one terminal of alternator field. The field is ONLY connected to the two brushes, it is a simple electromagnet. The "existing wire" at bottom going to the VR is the green. The VR controls grounding of the green to control output. You can replace that with a jumper to ground for testing. VR MUST be grounded.