Re: run Farmall 6V w/a 12 battery??

Posted by John T on October 25, 2005 at 16:23:38 from (66.244.90.98):

In Reply to: run Farmall 6V w/a 12 battery?? posted by PL on October 25, 2005 at 15:58:11:

PL, if you run it at 12 volts and it still has only a 6 volt coil AND NO ADDED EXTERNAL BALLAST RESISTOR ???? (if it has a coil ignition instead of a magneto which requires no changes as its not battery connected) the coil will run hot plus the ignition points will burn up prematurely. When converting from 6 volt to 12 and still using the original 6 volt coil, one must add an external series voltage dropping (12 to 6) power ballast resistor (rated around 1.5 to 1.85 ohms or so) after the ignition switch and ahead of the coil to prevent coil overheating and premature burning of the points. Or else just replace it with a full 12 volt rated coil.

True, a 6 volt gen wont keep her charged. I have used 6 volt gennys to charge a 12 volt battery by simply changing the 3 or 4 terminal Voltage Regulator (if it has one versus only a 2 wire Cutout Relay) to a 12 volt BUT AM NOT SAYING thats the correct or engineering proper way to do it, only that it worked. Its best to have a good genny shop convert it to 12 volts and use a 12 volt 3 or 4 terminal VR or one can still use the old 2 wire cutout relay system by replacing the Cutout Relay with a 12 volt unit.

Any working lights need, of course, to be changed to 12 volts.

The starter will work on 12 volts, although it may possibly be a tad rough on starter drives or flywheel teeth due the the higher kick in torque.

John T Nordhoff in Indiana, retired electrical engineer

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