John,
I tested it again. Then found 11.8 to 11.95V at the 2P connector (black to white wires). I really can't explain the difference in findings from before to now - but first i'll suspect operator error (the logical choice) First i though it was intermittent - and maybe it is, hence an open in a wire. But I was able to verify the voltage remained present with 3 plug/unplug cycles of the 2P and also wiggling the So the exciter voltage is present.
With exciter voltage present battery voltage is still 12V at battery, with existing VRR and STOC test VRR. 2P connector shows 3Ohms resistance from black to white - so should be ok.
So i think this confirms the alternator is DEAD, even though resistance and ground checks for the 3 yellow wires from the alt check out.
Maybe time to just start preparing for the 40AMP, if its going to be involved.