Make up some long jumper wires w alligator clips on each end (they come in very handy all the time) and jump directly to each connection/terminal duplicating Nacho's diagram & when (at a fast idle) you parallel jump the particular wire that has the open you'll hear the alt kick in then fix the open in that wire & unless there's been serious amperage that's cooked the copper inside or frayed/melted insulation on the outside (You'd visually spot that) or broken strands from excessive flexing (which is rare) wires do not go bad for no reason along their length but do so at the ends/connections so find the errant wire and check the end terminals/connections. EDIT unless the reg is bad but it is brand new & assuming it's grounded good. MORE EDIT w it all hooked up/fast idle, jump the alt male terminal (w the green wire) to ground & if it full fields then that only leaves the reg/reg ground/green wire as everything else is functioning good