Help with charging problem
 

My '65 912 quit charging while out on a afternoon drive, first thing I did after checking for lose wires was to replace the regulator, when I put the new reg on it charged for a few minutes then stopped. Then I took the generator to a local shop (that has a very good reputation) they tested it and said it was fine, put the gen back in and took them the new regulator and had them test it also to make sure I didn't get a bad one it tested fine also. I have cleaned every contact and ground I can find. Are there any ideas on how to diagnose this problem or possible fixes.

Thanks in advance

You might try polarizing the generator: disconnect both leads from the generator and remove the fan belt if installed. With the generator grounded, connect 12+ volts to the 'D+' terminal: the generator should run like a motor. Allow it to run for around 15 seconds. Just a thought...