Early Regulator Rectifiers that were fitted to these systems had a "Load Reference" connection that was joined to the battery when the ignition was ON, if there is a "Volt-Drop" to this wire the internal regulator would think that the battery voltage was LOW therefore it would allow the Voltage to rise above acceptable limits.

Later Regulator Rectifier units do not have this connection, if they are "over charging" the internal circuitry has failed, the unit must be replaced.

Under charging is more of a problem now though, we find that this is because there is a "Volt-Drop" between the Regulator and the battery, because the manufacturers are using wire that is not large enough.