Grounded Tach Wire Creates a Gremlin?

Dana67Dart said

My observation...

1. 21V is most likely a misread ov the , voltage meter. 2.1 or 0. 21 is most likely
2. The old style VR and alternator are wired correctly.
3. I admire your grounding, battery negative to engine block from block to dedicated welded post on frame.
4. The OP shows very normal voltages, battery with key on is a bit low. Some of the voltage drops are more than I would like but not causing the symptoms
5. OP states his ALTERNATOR guage is pegging on charge above idle.
   1. Causes for Alternator gauge pegging but voltage being normal
      1. Low battery
      2. High load

I ran my battery down till it would not start the car. I jumped it and drove around for 30+ minutes, the gauge was holding 1/2 way between center and full charge. Normally it will be there for a minute or so after the first start in a week.

I put the battery on a charger overnight and all was good in the world the next day.

Click to expand...

Switching batteries was going to be my next move. I read a lot before wiring this car, it's what prompted the new harnesses and sturdy grounds, it's easy to overreact fearing a mistake causing a melt down but with all the great input here im beginning to think the issue is simpler as you've described. Just like any other issue I have to keep after it. Thanks