Originally Posted by kenny61
You can get a coil with a built in ressitor. that what i did when i had to redo something once never had a problem
Not all 12 volt coils need a resistor. Some are wound to operate on 12 volts and have no resistor inside. Using one on a system that has a ballast resistor would have that 12 volt coil running on 6 or 7 volts and could cause ignition problems.