Alternator on a Farmall MD

Single wire units place a small amount of drain on the battery when stopped. Not an issue if you run the engine frequently. But if you let a single wire alternator equipped engine sit idle for a couple months or longer, most single wire units will flatten a good battery unless the ground cable is disconnected.

I have seen guys use GM 10 SI alternators on diesels and they excited them by running a hot wire to some sort of a normally open oil pressure activated switch (think thats what they use) that closes upon oil pressure. They take the switched output from the Normally Open oil pressure switch with a 10 ohm resistor to the lil No. 1 terminal on the side of the alternator to excite it. The lil No 2. terminal, of course, wires direct to the alternator output.

Let us know, good luck n God Bless

John T

Be aware however when single wired an alternator will need to be spun up to higher RPM at startup to get it to begin charging. On a slow turning engine like the MD you may find you'll have to change to a smaller pulley to make the alternator spin fast enough to energize at startup.

A simpler option may be to stick with the 3 wire setup and install a normally open oil pressure switch on the engine (switch contacts close on dectecting oil pressure). Run a wire from the alternator BAT terminal, through the pressure switch, and back to the alternator #2 terminal and you'll be good to go.

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