69 Dart - overcharging issues
I always divide this into sections
Wiring problems in the charge wire (output)
Wiring problems in the field circuit
Problems with grounding
Alternator problems
VR problems
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It would be rare but "could happen" that a VR would cause troubles like this
Check:
At night or in the dark, look around different angles into the alternator. You may have to turn on the heater blower to load it. "Play" with the throttle. Look for odd sparking inside. Identify the brush sparking, they should be easily identifiable, and "steady."
But if you see odd sparking that comes and goes, it might be the stator has worn insulation off the windings, or even broken loose connections at the diodes, etc
Be absolutely CERTAIN the VR is grounded.
Try "rigging" a temporary wire that you can disconnect, so you can drive it this way for test. Run a solid wire from the starter relay battery stud to the IGN terminal of the VR, and run it long enough to see if it makes a difference.
See if you can "Rig" a voltmeter to the alternator output stud. If this voltage goes way high but the battery does not, this indicates a bad connection in the charge wire circuit.