When I was changing my Mopar flattie over to 12 volt, I got an article off the internet and it said if you are using a modern 12 volt aftermarket coil, you do not need a ballast resistor because it is built into the coil. Well, I smoked the coil last night so i'm wondering if I do need one or how I can determine if I need one. It was a new coil and only ran a handful of times. Anyone have any experience with this?