transtar61
Member
Just asking changing my farmall super c to 12 volts i'm going to use a 3 wire alternator . What i wanted to know is a diode or light needed from the wire runs to the kill switch . Thanks for any help. Scott
- Thread starter transtar61
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Bob M
Well-known Member
Yup... you need either a diode or lamp in the wire between the ign switch and alternator #1 terminal. A 1N1004 or equivalent diode wired with the band end toward the alternator works well. Or a #168 auto side marker bulb.
I prefer the lamp myself - it works as a charging system warning light.
I prefer the lamp myself - it works as a charging system warning light.
A diode or indicator lamp will work equally well in the "excite" circuit to the alternator's #1 terminal.
I use 1N5408 diodes, they are overkill at 3 Amps, 1000 PIV, but are CHEAP (less than a buck on-line), and don't fail in use as small units occasionally do.
The lead from the cathode (white banded end) goes to the alternator's #1 terminal.
If using a lamp, it has to draw enough current to "excite" the alternator, meaning that a "tiny" lamp or LED won't work.
Some OEM setups used a lamp and a resistor in parallel, meaning that if the lamp fails, the system will still excite and charge.
So, your choice, there's "more than one way to skin a cat"!
I use 1N5408 diodes, they are overkill at 3 Amps, 1000 PIV, but are CHEAP (less than a buck on-line), and don't fail in use as small units occasionally do.
The lead from the cathode (white banded end) goes to the alternator's #1 terminal.
If using a lamp, it has to draw enough current to "excite" the alternator, meaning that a "tiny" lamp or LED won't work.
Some OEM setups used a lamp and a resistor in parallel, meaning that if the lamp fails, the system will still excite and charge.
So, your choice, there's "more than one way to skin a cat"!
The CHEAPEST easiest component to prevent ignition run on is a 10 ohm or so 5 watt carbon resistor,,,,,,,,,,Maybe a 3 to 5 amp diode is next cheapest,,,,,,,,,,,,A small 12 volt indicator lamp (NOT an LED) is pretty cheap n easy,,,,,,,,,,,,and Bob M's method of a lamp plus resistor in parallel is handy in case the lamp burns out. YOUR MONEY YOUR CHOICE I have seen some tractors (IF they idle slow enough) that didn't require any backfeed prevention.
John T Live from a ranch in Coleman Texas
John T Live from a ranch in Coleman Texas
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