Ballast resistor

flyntl39

New User
My old Jubilee tractor was converted to 12 volt system when I bought it. When doing some work to replace the distributor oil tube, I checked the resistor located between the ignition and the coil. Either end of the resistor shows 12 volts when the ignition is switched on. I assumed that the resistor was placed there for use of a 6 volt coil but it appears that 12.6 volts is being supplied to the coil. The resistance across the resistor is 1.2 ohm. Can I remove the resistor from the system?????
 
If the points were open and the engine was not turning, then there was no current going through the resistor, and so the voltage relative to ground will be the same on both sides of the resistor, as a voltage drop only occurs across a resistance when there is current flowing. Measuring 1.2 ohms of resistance across the resistor shows that it is still working and good (anywhere from 1.2 to 1.6 ohms should be fine). If the tractor is working fine with it there, then I would not remove it, as it is likely to burn up the coil without the resistor in place.
 
Simple answer is yes you can remove it but if you do so the points will not last near as long as they do now and the coil may not last very long either.
Bet if you had looked when you did the voltage reading the point where open and so with point open the circuit if open so you read battery voltage
 
Let me see if I have this right. Most point systems and a lot of early electronic ignitions have/had ballast resistors to keep the current through the coil low and to keep from burning the points.
But during cranking the ballast resistor is bypassed to make sure the engine will start. Once the ignition key is released or the temporary toggle is released the ballast resistor is no longer bypassed.
 
On that tractor the 12 volt is a conversion from 6 to 12 volts so there would not be a ballast resister by pass on it like what is sen on many newer machines
 
When and if you have to replace the coil, replace it with a true
12V coil. One marked "No external resistor required" or similar.
NAPA IC14SB for example.
Once you do that you could safely remove the resistor.
I don't have anything against the resistor being in there, but it
is a couple of extra electrical connections to corrode and another
part that could "possibly" go bad some day.
 
12v on both sides of resistor means no current, points are open or coil is open. When points are first closed my jubilee shows 6v on coil, 6v on ballast and 4 amps. Make measurements fast, because as the resistor heats up, it increases resistance.
 
Old, this is the coil i have installed in my tractor...12V coil. "No external resistor required"

(NAPA IC14SB), i have bypassed the resistor, are you saying you would install a resistor to ensure longevity of points and coil?

thanks dave
 
If the coil says no external resister needed then you do not need a resister in the circuit
 

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