Here are a few notes on Pertronix electronic ignition systems and their effect on coils. It's neither a drawing nor a schematic but I repeated it here to make the resistor calculator easier to find.:
Through testing and following an advisory from Pertronix regarding a 4 amp system maximum we found the addition of a ballast resistor in the ignition primary circuit significantly reduced coil heat in some cases. Internal coil resistance combined with coil input voltage were found to be consistent predictors of coil heat and subsequent failure. There is no indication a resistor will fix a sick coil. If your coil has overheated to a point of shut down, it's damaged internally and needs replacement.
We now have a simple ballast resistor calculator specific to the Atomic 4 with Pertronix electronic ignition. It applies what we've learned on the lengthy Coil Input Information thread and adds a 15% safety factor. You need to input two values, it provides a resistor value to one decimal place. Note that this is the best information we have at this time. Should new info emerge, we'll adjust the calculation as necessary.
Ballast Resistor Calculator.xls
For those unable to open the calculator or without Excel, smosher provided a free program to resolve the issue found here.
Through testing and following an advisory from Pertronix regarding a 4 amp system maximum we found the addition of a ballast resistor in the ignition primary circuit significantly reduced coil heat in some cases. Internal coil resistance combined with coil input voltage were found to be consistent predictors of coil heat and subsequent failure. There is no indication a resistor will fix a sick coil. If your coil has overheated to a point of shut down, it's damaged internally and needs replacement.
We now have a simple ballast resistor calculator specific to the Atomic 4 with Pertronix electronic ignition. It applies what we've learned on the lengthy Coil Input Information thread and adds a 15% safety factor. You need to input two values, it provides a resistor value to one decimal place. Note that this is the best information we have at this time. Should new info emerge, we'll adjust the calculation as necessary.
Ballast Resistor Calculator.xls
For those unable to open the calculator or without Excel, smosher provided a free program to resolve the issue found here.
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