Posted by John T on June 02, 2010 at 10:59:56 from (66.244.97.31):
In Reply to: Diode posted by JD2840 on June 02, 2010 at 10:40:23:
The diode is used to prevent the alternator from backfeeding the ignition coil so when you turn the switch off the tractors STOPS running.
About any diode rated at say 3 amps (a bigger rated is okay if thats all you have like a 5 or 10 amp or more) and with a voltage withstand rating of say 50 volts or more (again a higher voltage rating like 100 or more volts is okay) will suffice. NOTE its polarity sensitive and MUST be wired correct, the cathode towards the alternator assuming Neg ground.
I have used a 10 ohm or so (or larger) resistor instead of a diode as it can still prevent the backfeed run-on problem PLUS provides at least some degree of safety current limiting.
It (excitation circuit with diode or resistor) wires between the ignition switches IGN output or the ignition coils input (same electrically) and the small No 1 alternator terminal. I wire the other No 2 small voltage sense terminal direct down to the alternators big main output stud
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