By this do you mean the big post is "low," 11-12V instead of 14? Or is it actually "zero" volts? That stud should ALWAYS be hooked to the battery. If it has no voltage, there's a break in the wiring.
Hey Big Block,
make sure the voltage regulator and both alternator field wires are connected when checking voltage at the big post on the alternator or battery. Also, double check your wiring at the firewall connector, especially the wires that go to the ammeter and ignition switch.
