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Message: <blockquote data-quote="MaxW" data-source="post: 57617" data-attributes="member: 7705"><p>As I understand, Series Wound starter motors will always spin the same direction with forward or reverse polarity. It's the relationship of the field polarity to the rotor polarity that determines the rotation. This is why winch motors use four solenoids to flip the field when changing direction. The little mini-starters are permanent magnet motors and they would work different and would spin backwards if reversed. At least that is my understanding. As for reversing the polarity and blowing up the alternator, it's the diodes that create the short when the wiring is reversed. Inside alternators there is a three phase stator, on each phase there are two very large diodes one going to the positive terminal and one going to ground. With two diodes per phase, and three phases, that's six high amperage diodes. When the battery is reversed those six diodes are reversed and the battery shorts through those diodes until the battery is dead or the diodes melt. Visit any alternator rebuild shop and they will show you examples of melted diode packs.</p></blockquote><p></p>