I'm working on the charging wiring on my Bene 331 and while tracing the output of the Yanmar 3GM30F's alternator, I see that both wires from the alternator go to a little black Bosch cube maybe 1.5inches on a side. Two wires go out of the cube, one to the starter (presumably the ground), and, sorry, I didn't finish tracing where the positive went. Any idea what this box does? It looks like a relay.