ALTERNATOR OUTPUT

Here's how a '68 Dart alternator was wired from the factory.

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The regulator allows current to flow through when it (the regulator) sees less than 14 volts at its 'ignition' connection.
Ignition meaning the ignition-run wiring. How it works is illustrated here.

Possibilities for power continuously flowing into the rotor include: regulator seeing low voltage due to resistance, and regulator getting bypassed (J2A wire connecting to the alternator field terminal somehow)