Alternator - regulator mismatch?

Your regulator needs a non isolated field (one field wire) typically the round back alternators are non isolated field and have only one wire from the mechanical regulator. FYI, newer 1 field wire regulators available today are internally electronic.


You can use a square back alternator with a mechanical regulator if you ground one of the field terminals on the back of the alternator.

SOME rebulders have been known to internally ground one of the square back field terminals to make it compatable with older cars.

The alternator in your first photo has a ground wire from one of the field wires to ground.

As others have said you can use an electronic 68? and up regulator with some wiring changes.

Assuming you have the correct alt for your regulator, your old mechanical VR might have finally given up (I would suspect that the contacts are stuck closed if you are over charging)