I purchased the same upgrade from Hall as you and went through the same frustration. What the instructions do not tell, at least they didn't when I did it a year ago, is to remove the inline resistor on the back of the Tach for the charge light. As I recall, the Hall kit uses the blue/black wire as both the 12v+ and sense for the alternator. As soon as I bypassed the resistor, voila, my system was able to charge. The light no longer works, but you don't need it.
Hope this helps.....
-Richard
'71 #1731
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