Any regulator mounted on the body of the car needs a good ground. Some time ago, one of my students was having repeated battery failures on a Dodge pickup with an electronic regulator. The batteries would boil dry, and sulfate to the point they could not be recharged, even after adding water and cycling the charge up and down several times. We found that the charge voltage was going to over 17 volts anytime the lights were turned on. Adding a ground wire from the body to the engine solved the problem. The lights were finding a ground through the regulator wiring, and putting the alternator into full output in the process.
Jerry
