I dont know what diode trick you tried but i have always been able to get regulator voltage up .5 volt by putting a diode in the wire to D+,perhaps there is something different about your alternator but it has always worked for me.you are aware that the diode has to be placed in the correct polarity? Connect the diode to the wire that goes to D+ and use a test light to be sure the voltage is getting thru the diode before you connect to the D+ terminal. My $.02 Don

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