Can anyone tell me what the resistance should be for the oem ignition
resistor? Also what should the ohms read for the proper ballast resistor? The one I bought at NAPA is rated .50-.60 ohms. This is on a 12 volt conversion. Only knocking volts down to 10 volts on a 6 volt coil. Having issues with the tractor running for a while then dying with no spark. I also tried replacing the oem resistor with a China brand bought on line.

The China model gives a reading of 7.4 k ohms. The oem read .7 ohms. This is on a 8N motor front mount distributor in a 2N tractor. I'm about at my wits end with this issue.

I've replaced the points, condenser, distributor cap, new coil, and the resistors mentioned above. Got it started last evening, then it wouldn't start with no spark at the plugs once again. I put the oem ignition resistor back on and now it is running at this very moment. Just waiting to see how long it takes to die.
 
Can anyone tell me what the resistance should be for the oem ignition
resistor? Also what should the ohms read for the proper ballast resistor? The one I bought at NAPA is rated .50-.60 ohms. This is on a 12 volt conversion. Only knocking volts down to 10 volts on a 6 volt coil. Having issues with the tractor running for a while then dying with no spark. I also tried replacing the oem resistor with a China brand bought on line.

The China model gives a reading of 7.4 k ohms. The oem read .7 ohms. This is on a 8N motor front mount distributor in a 2N tractor. I'm about at my wits end with this issue.

I've replaced the points, condenser, distributor cap, new coil, and the resistors mentioned above. Got it started last evening, then it wouldn't start with no spark at the plugs once again. I put the oem ignition resistor back on and now it is running at this very moment. Just waiting to see how long it takes to die.
The theoretical resistance of an OEM style resistor when the engine is running is 0.5-0.6 Ohm. But you cannot measure that with a meter. Brand new out of the box cold (room temp) on all I have measured has been 0.1 Ohm. Most often in posts on this board you will see numbers like 0.3 cold to 1.7 hot. The resistor is temperature dependent, it acts like a positive temperature coefficient thermistor. The purpose is to allow higher current for starting while voltage is lower due to the starter motor and then taper off to a safe level for running to protect the points and coil.

The total primary resistance should be such that current is limited to 4 Amperes. On a 6V system that is 1.5 Ohms. On a 12V system it is 3 Ohms. A 6V coil for a front mount distributor should have a primary resistance of about 1 Ohm. A 12V coil for a front mount distributor should have a primary resistance of about 2.5 Ohm. Add 0.5 Ohm from the OEM resistor and that is what you get.

You say you have a 6V coil and a 12V system. In that case you need to add an additional voltage dropping resistor of 1 to 1.5 Ohm to get the target 4 Amperes. OEM resistor is still needed. Easier to just use a 12V coil.

Tractor running for a while then dying with no spark could be several things. 3 to 5 minutes, condenser. 1/2 to1 hour, coil. Random, ignition switch.
 
Last edited:
The theoretical resistance of an OEM style resistor when the engine is running is 0.5-0.6 Ohm. But you cannot measure that with a meter. Brand new out of the box cold (room temp) on all I have measured has been 0.1 Ohm. Most often in posts on this board you will see numbers like 0.3 cold to 1.7 hot. The resistor is temperature dependent, it acts like a positive temperature coefficient thermistor. The purpose is to allow higher current for starting while voltage is lower due to the starter motor and then taper off to a safe level for running to protect the points and coil.

The total primary resistance should be such that current is limited to 4 Ohms. On a 6V system that is 1.5 Ohms. On a 12V system it is 3 Ohms. A 6V coil for a front mount distributor should have a primary resistance of about 1 Ohm. A 12V coil for a front mount distributor should have a primary resistance of about 2.5 Ohm. Add 0.5 Ohm from the OEM resistor and that is what you get.

You say you have a 6V coil and a 12V system. In that case you need to add an additional voltage dropping resistor of 1 to 1.5 Ohm to get the target 4 Amperes. OEM resistor is still needed. Easier to just use a 12V coil.

Tractor running for a while then dying with no spark could be several things. 3 to 5 minutes, condenser. 1/2 to1 hour, coil. Random, ignition switch.
4 Ohms of "primary current" eh?
 
Thanks for your replies. I think I need the additional voltage dropping resistor with the 1 - 1.5 ohms. I replaced it but I mistakenly installed another ballast resistor. Now it has the oem ballast and a ballast resistor from. NAPA. Where can I purchase the 1- 1.5 ohm resistor? The guy at NAPA said the .5 ohm ballast was what I needed.
 
Most auto supply resistors don't even have a value listed. The small resistance values are difficult to accurately measure. Here are a few, but I have found trial and error is about as good as you can get.
ballast resistor values
NAPA* Echlin* ICR11 (1.35 Ohms)

NAPA Echlin ICR23 (1.2 Ohms)

NAPA Echlin ICR34 (1.4 Ohms)

Lucas* 3BR (1.3 - 1.4 Ohms)

Mopar* DCC-4529795 (1.4 Ohms)

Accel* ACC-150250 (1.35 Ohms)

Standard* RU-4 (1.35 Ohms)

Standard RU-23 (1.2 ohms)

Standard RU-37 (1.4 Ohms)
 
As I tried to say, caution is in order. Just now, I visited this and two other well known tractor parts sites and all 3 sell resistor 8NE10306. They state values of 0.6 Ohms, 1.0 Ohms, and 1.6 Ohms. No one know what you get :( until you buy one and measure it , if you can.
 

We sell tractor parts! We have the parts you need to repair your tractor - the right parts. Our low prices and years of research make us your best choice when you need parts. Shop Online Today.

Back
Top