Farmall B BN would not shut off.

Brad_bb

Member
Been doing some revamping on my Farmall BN (John's forklift conversion). I love this machine! I had the alternator rebuilt- 2 blade plut and post Delco Remy(internal voltage regulator). After installing this and running new wiring to replace the old ones with cracking insulation, I started the tractor but it wouldn't shut off. Now I'll admit I screwed up and hooked up a new battery backwards and melted the insulation on the 2 main power wires, thus necessitating the complete rewiring. The terminals were reversed on the new battery and I wasn't paying enough attention. Had the alternator checked at the shop that rebuilt it and they said it was not damaged. I replaced the coil. Still wouldn't shut off. I have an on/off switch on the dash that when turned on, gives power to the starter button. I also have a master battery shut off switch. When I shut off the battery the engine would continue to run. The coil was pulling from the alternator to continue to run. Talking to the Starter/Alternator shop, he suggested installing a diode in the wire that was feeding back to the coil. A diode only lets current flow one way and not the other. He gave me one and I installed it in line with that wire that connected to the coil as he instructed and it worked. So if you ever run into that problem, this is something to keep in mind.
 
For sure a diode will work, that topic has been covered on here a gazillion times lol. However I used other methods such as 1) A simple resistor that is cheaper, reliable, and doesn't require the correct polarity connection,,,,,,,,,,,,2) A small incandescent Idiot Light charge indicator that goes off to indicate charge plus stops run on,,,,,,,,,,,,3) A combination idiot light plus resistor that works even if bulb burns out

John T
 
John T you are correct, my guy also told me that an indicator light usually has enough resistance to drop the voltage enough in that line that the tractor will shut off when the switch is turned off. Also said you should be able to use a resistor or anything that is going to draw off the backfeed from the alternator enough to kill the tractor and it doesn't take much.
 
An "Idiot Light" is great because it does BOTH it provides a visual charge indication when it goes off PLUS its resistance drops enough voltage so the coil doesnt get enough backfeed to keep the tractor running with ign OFF. However you need to use an incandescent light NOT an LED. Indeed I know I'm right cuz I did it that way for yearssssssssssss being a used tractor dealer years ago. A simple resistor is easiest and cheapest though versus a more expensive diode which MUST be wired at the correct polarity,

John T
 

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