I have voltage reg that came on my 40 ford that looks brand new on the inside but won't work. Took gen and reg to repair shop guy said gen fine reg no good what makes a reg that looks new on the inside go bad, put new reg in car all good. Why can't it be fixed?
Regulator contacts on cut out or voltage reg or current regulator could be pitted and burnt. Any of the winding coils on the three bobbins could be open circuit (broken) or resistors broken. There was a time when these internal regulator parts were available as spare parts (1950s or 1960s) but not now. Needs a trained eye or some expertise to be able to test these issues. Regards, Kevin.
The Echlin VR-402 was the common NAPA 6-volt replacement and wasn't a bad unit in its original form but they weren't really made to be repaired either. They could be adjusted but that was about it. The modern blue ones are likely made in Mexico or Asia and aren't the quality of the old original black cover part. The original OEM parts from Ford were very good units and could be repaired. Stuff had screw hardware in some cases so a pole coil could be removed. Modern stuff is all riveted together and has light duty sheet metal or plastic for some of the supports and pieces.
A part that has been kicking around on a parts store shelf for 50+ years may have had a problem when new or it may have had some deterioration such as corrosion that rendered it inoperable. The resistors are generally mounted on the underside but are open to the elements if the box gets compromised.
