is a resistor needed in a 12 volt system

I have a 1926 coupe that has been modified to a 12 volt system with a distributor. I am having a problem with burning out the coil. I have relocated the coil to the firewall to keep it from getting as hot, but I have heard that you should use a resistor to keep the coil from burning out also. Does anyone have any experience with this.

Check the markings on the coil, often they are marked “requires ballast resistor” if one is needed. Based on yours running hot and burning out, it sure sounds like it needs a separate ballast resistor. You can get an old Chrysler two-prong resistor from a junkyard or the parts store and temporarily wire it in line with the primary feed to the coil to see how the car runs with it.

If you really want to get fancy, you can wire up a switch to bypass the ballast resistor for a hotter spark during engine starting, then flip the switch and run with the ballast resistor in the circuit for normal driving. :slight_smile:

Most do need one. The T part sellers carry some Chinese made 12Volt coils that say “No Ballast Resistor Required” on the side. But they burn out quickly without a ballast resistor. So I suspect it’s a marking that is in error.