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Bryan, BALLAST RESISTOR QUESTION If you are going to use a new "full 12 volt" rated coil, then you do not need any external ignition ballast resistor, they are only required when you use an exisitng 6 volt coil on a 12 volt tractor. CAUTION be sure that so called 12 volt coil is NOT one labeled "For use with external ballast resistor" as some are, you need a plain old full 12 volt rated unit NOTE: That 10SI Alternator is for Negative ground, are you already set up that way?? If you were at Positive ground you would have to reverse any ammeter leads (if it has one) and wire your new coil to match the Negative ground i.e. its lil + terminal receives voltage from the Ignition Switches IGN output when ON, while its other lil - terminal goes to the distributor. DIODE QUESTION That 10SI alternator is actually a three wire device (has big output lug on rear and 2 lil No. 1 and No. 2 terminals on side) which requires excitation voltage on No. 1 and voltage sensing on No. 2, and thats where the wiring and "Diode" you mentioned come into play so its all wired up and functioning similar to a one Wire Alternator. The reason when a "Diode" (one way curent flow check valve) is required, is if and when you use an excitation voltage feed off the IGN swiches output terminal (feed down to coil) to excite the lil No. 1 terminal on the alternator,,,,, its possible that when you turn the ignition switch OFF, the tractor keeps running cuz the coil is backfed from the alternator. The Diode (one way curent flow check valve) prevents that. To better protect the alternators internal diodes, I also recomend a 10 ohm resistor in that excitation voltage circuit from the Ignition switch down to the lil No. 1 alternator terminal. NOTE some people dont use a diode but an ON/OFF Toggle switch to accomplish this and some people feed the excitation circuit elsewhere then the coil or ignition such a son a Diesel application. The lil No. 2 terminal on the Alternator simply wires up to the big main output post on the alternators rear. In case the wiring description below cornfuses you, e mail me at [email protected] and I can return e mail you a wiring diagram for using a GM 10SI Alternator. WIRING Run a 16 Gauge or so wire from the Ignition switches IGN terminal (what feeds the coil when ON) with a series 10 ohm 5 watt resistor and a 5 amp 50 PIV Volt Diode (IT MUST be wired + anode end to switch, - cathode end to alternator) to the lil No. 1 terminal on the Alternators side. (Excitation circuit) NOTE these ratings I use are a tad bigger than actually required, but the higher rated units have bigger leads easier to wire up. Run a 16 Gauge wire from the Alternators lil side No. 2 terminal jumped up to the big main rear output post. (Sensing circuit) Run a 10 Gauge wire from the Alternators big output post up to the Load (NOT to battery) side of ammeter (if it has an ammeter). If theres only a 12 Gauge wire from the ammeters other Supply terminal to the battery or starter etc., I replace it with a 10 gauge. John T Nordhoff in Indiana, retired electrical engineer
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