Farmall Cub

Up date, I measured the voltage on both sides of the coil with the engine off and the points open and the voltage is the same on both sides 12.3; so I guess I need to install a ballast resistor in line on the distributor side of the coil is this correct or does it matter?

ok, even if your cub is 12 volt it requires a coil with a built in resistor. This resistor will drop the voltage to around 6 volts. even if you install a balast resistor you have to be sure it is the right one to drop the voltage. useually a early 60's resistor for a chrysler product will work.one way to tell if you have tooo much voltage to the coil is it will get tooo hot to touch in 10 minutes or so. it should get warm not hot.It may not be your coil at all it may be the distributer shaft. the bushing may be worn to the point where the points wont open or close correctly. you will never get a correct voltage reading when the engine is runing for reasons already stated. also if your 12 volt cub has the correct regulator and wire harness the ignition runs through the voltage regulator . L terminal.

Thanks, I do not have a "voltage regulator" as it has been converted to a one wire alternator; there is play in the distributor shaft and it had never been lubricated before I took possession of the little darling so I suspect that the bushing is wore, here I go again.

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Above, discussion on Chrysler resistor. The resistor can be purchased at auto parts stores. Last time I purchased one it cost in the $3- range. Much cheaper than purchasing a new coil.

The store may have the resistor available in different Ohms. Select on around 2.3 ohms, or as close as you can get. Ideally the resistor's Ohms should be identical to the coils primary resistance/Ohms.

I guess I need to install a ballast resistor in line on the distributor side of the coil is this correct or does it matter?

Doesn't matter.

I had two cubs in the last 4 years that the owner could not get it to run right at all. He knew his cubs too. I have to admit i too was a little stumped. then I found a lot of slop in the shaft. fixed that. still running great. Also last summer a friend had a later model yellow cub he could not get it to run on 4 cylinders,only on 3. turned out one of the point cam lobes was worn off. first time I had seen that.

Thanks, Great info, I'll be looking a little closer at the distributor...

SeanW wrote:Up date, I measured the voltage on both sides of the coil with the engine off and the points open and the voltage is the same on both sides 12.3; so I guess I need to install a ballast resistor in line on the distributor side of the coil is this correct or does it matter?

With the points open you have no current flow, so those voltages would be the same with or without a resister. With a 12 volt system you either need a coil with a built in resister, or a separte resiter to drop the voltage, but either way, with the points open all the connections will read 12 volts.

OK, I installed a resistor and the voltage did not change, I started it up and it ran just fine, with little or no change....I did move the distributor shaft and there is play, my be 10 to 15 thou....but like I said it seems to run OK....
Love the feed back, lots to learn...Sean