No Output from Alternator

Well, damn it. I just replaced the original 90amp Nippondensu with a new remaned Autolite 120amp Nippondensu this summer. Now, it just stopped producing voltage all of a sudden. I'm going to switch the connection back to direct, instead of through the isolator to see what's going on, but I'm about as clued in as a log.

Any home methods of testing the alternator to see if its bad, or did my SMEC's voltage regulator take a dump? If its the alternator, it's still under warranty, but if its the SMEC, I'm gonna be ticked.

It was fluctuating earlier today, losing charging, regaining, losing, repeat. I then unhooked the negative terminal and replaced the clamp fitting to make certain there wasn't a loose fitting. Worked fine for about two hours, then going down the exact same onramp to the free way, it crapped out and stayed crapped out. The truck drove home on its battery.

Anyway, any other spots to test? I'm frankly stumped and PO'd.

For the records, its a 1992 Dodge W250 with the 5.9L V8 Gas (TBI), using the older SMEC control model (the one with the air hose connected to it from the intake line).

EDIT: Oh, yes its also throwing Code 41 - Low Voltage Detected at ASD Relay, check Charging System (Lot of bloody help that error code is).

fields getting power?

What should the two posts on the back of the alternator be reading if their in normal operation? I've got to go pickup a new multimeter tomorrow, but I'm at the point where I'm eliminated everything else, except for the two little wires that go to energize the alternator and regulate the voltage. All the primary wiring I've ruled out by process of elimination. Alternator I took back to the store and had swapped under warranty and the diode based Isolator in the system was unhooked and replaced by a constant duty solenoid to break the contact between the camper battery bank and the truck's starter battery. Right now, its disconnected so it can't energize and connect both banks, ruling out problems from the RV battery bank.