Fluctuating neg. to ground on ignition coil

You can run a stock coil for awhile without the ballast resistor and it will work, if you want to do that to troubleshoot. Just jumper it.

The previous owner of my car ran an unintended full voltage coil life experiment. He the ballast wired incorrectly, so it got full voltage when it was running, and had the ballast in the circuit when it started. He drove it that way for about 4 or 5 years. He said he had to replace the coil about every six months. From this data it appears that it will take awhile (maybe tens or hundreds of hours) for a coil to fail at full voltage.

When I got the car I figured it out after he told me about the routine coil failures.

I am not saying you couldn’t possibly do so damage to the coil doing this, but that it is probably unlikely for the time it takes to drive it around to see if that fixes your problem.