I know this thread is over two years old, but:
The AC terminal of an alternator (if expicitly provided) is a 12-pulse-per-revolution tach output. That's it. The load dump controller is simply a box that watches the Alternator revs and based on its setting, will dump non-critical loads if the alternator is not spinning fast enough to generate the power to support those loads + the critical loads. The tach output can also be used to drive, well - a tachometer. When set with the correct ratio (alt-pulley vs. crank pulley) the alt output frequency will indicate the engine RPM on an electrically signalled tach. I have a 200A C.E. Neihoff in my bus conversion (another forum I paticipate on), and I use the AC output for my tach.