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12SI Altenator upgrade problem

937 Views 6 Replies 4 Participants Last post by  CHELKAMINO
Did this upgrade 3 years ago on my 71 with no problems. Just did the same upgrade on the 72 Elco and it starts and runs fine, but the motor will not shut off with the key? I have an ignition switch for the MSD box, so I can kill it that way. I wired it correctly and looped the old regulator harness per MAD's web site instuctions.
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You need a diode in one of the lines from the alternator. The MSD website has instructions..

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