VintageMopar wrote:
The regulator is held by cadium plated bolts and star washers for a reason. It must be grounded well or you get 18 volts.
The green wire from reg goes to alt brush, if this is grounded anywhere you get 18 volts. Just unplug reg and if it drops to 12 volts to check for that
Quyana cakneq (a Yup'ik phrase meaning "Thank you very much") for your very important addition to this discussion. I forgot about the possibility of a faulty regulator ground. (As with many experienced people, I sometimes forget about the ground side of circuits.)
More importantly, I didn't know (or realize) a faulty regulator ground would cause the regulator to overdrive the alternator. (i.e, cause the electrical system to go to 18v) Now that I think about it, it makes sense. The sensing circuit within the regulator needs a good ground to identify system voltage. A faulty ground would cause a regulator to sense very low or non-existent voltage in the system, causing it to keep the alternator field energized.
If I recall correctly, regulator replacement usually includes applying dielectric grease between the back of the regulator and the metal it's bolted to. This would serve to prevent corrosion and ensure a good electrical connection between the regulator and the vehicle ground.
I also recall that some people, decades ago, ran a dedicated ground wire to regulator case/mounting bolts. (Mainly because a vehicle's chassis and body aren't always the best ground system.)
