Alternator Wiring

[alga]

Today it took me an hour or two to get my Hitachi alternator off a Nissan Sunny to charge. I even took it apart again to look for some obvious failures.
Apart from the charge cable, it's got two wires going out of it: L (dashboard charge light) and S (sense, ignition +). I hooked up the wires, but no voltage appeared on the BAT pin. I almost declared it dead, but tried switching the wires around. BAM! 43 volts on output! Turns out, I connected the dashboard light has to ground instead of the ignition +, that prevented the alternator from charging.