Coil - resistor compatibility question.

If you have what is in the picture in post 6, you basically have a stock Mopar electronic ignition. With a 1.5 ohm coil, you should use the stock ballast resistor.

The real issue with matching coils, ballast resistors, and ecu’s is current, which is not easily measured without sophisticated equipment. The current varies with time, so a dc current meter will not give the right answer.

As I recall, the stock Mopar ecu is designed to drive about 5 amps (or close to that). That means, at ~14v, you need about 3 ohms to get a 5 amp current.

If your coil is 1.5 ohms, you need about a 1.5 ohm resistor for a total of three ohms.

If you had an 3 ohm coil, you could probably get by without a ballast resistor. (Maybe)

The thing to keep in mind is that ignitions are designed as a “system” and if you start changing parts, you better follow manufacturer recommendations or you are on your own.

Also keep in mind that cheap meters are not very accurate at measuring low resistances, like 1 ohm.