Ballast Resistor question

[Wildergarten]

Wildergarten: if input V is 14, coil primary resistance is 1.41, and other variables constant, what would the current at peak voltage be if BR is either 0.5ohms or 1.79ohms?

The best way to get that number is with an oscilloscope.

[swptln]

Well, if you do the math/Ohms Law. The FSM is wrong, there is no way your going to have a 3Amp load, with engine not running. That is a static load, so the math/Ohms Law works I=E/R. The running load is going to be different and the math/Ohms Law won't work, as mentioned in the FSM, the load is going to be a lot less. Your going to have a increase in voltage drop across the points because it's a poor connection, intermittent, arcing, carbon build up, etc. So, even though you may have 13-14 System Volts while running, you are not going to be putting that much voltage to the coil. Running the .5-.6ohm ballast resistor is just going to shorten your coil and points life.
This why point type ignitions were eliminated in 1972-73, it's much more efficient to control a coil with a ECU or magnetic pickup and relay. Will handle more rpms, gives more consistent spark, less maintenance.

[Jims68]

OK.... now first I have to say, I am NOT trying to beat a dead horse with this subject. BUT... I found this page informative and mentions about ballast resistors and how coils work with condensers etc. YES, it says it's for lawn tractors... but pertains to everything. It gives a link on how to check the OHMS resistance on a coil etc. LOOK for the FLASHING IMPORTANT word.

Check it out!

http://gardentractorpullingtips.com/ignition.htm