We are swapping out the failed alternator on our 83, and the old alternator is has the normal voltage regulator, and the socket for the plug from the car, but it also has this strange little flat black box with a wire coming out of it that plugs into an additional terminal on the back of the alternator. We are wondering what this is/if we need it on the new one, as the new one simply has the regulator and has an empty pin socket where the little box plugs in on the old one. What is this little thing? We can't find a replacement item for it anywhere.....so do we even need it or is it important?

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