I have a 57 Ford Fairlane. The car started to run rough and missing when I drove it . I got home on a prayer and it died at the garage door. It had no spark and the coil was crazy hot. I checked the voltage at the coil resistor, It was the same voltage in and out. Is that correct? I thought it reduced the voltage also? I put a coil for that make ,model and year on it. It starts and the voltage in and out of the resistor is the same. Is it good to go? Thanks
I always understood that the ignition resistor reduces the voltage to 9 volts except when starting. The resistor is by-pased when cranking the engine.
You need a ballast resistor if/since the coil calls for it. Check the resistor by disconnecting from the battery and measure the resistance through it with a multimeter. It should be 1.3 to 1.4 ohms. Higher or lower it should be replaced. If it is bad it can cause the points to burn as well. I use a Pertronix module instead of the points and a Pertronix coil that doesn't need a ballast resistor.
If you've got a points distributor, check you're points and capacitor. The points being open will let you see the same voltage on both sides of the resistor. ( nothing wrong with that). A bad capacitor will cause you're points to look closed all the time and heat the coil because it can't collapse. If it ran before and you didn't have trouble check the components you have, don't re-engineer your ignition setup.
My advice would to get rid of the points and resistor and install the Petronix module and coil. You can buy the module for less than $100.00 and forget about all the problems with points burning and constantly adjusting them. The Petronix is really easy to install. I did it 3 years ago and it works out really well.