With 12.14 volts coming from the ignition switch and a 6.59-volt drop occurring across the resistance wire, 5.55 volts would now be measured at the coil (+) terminal (12.14 - 6.59 = 5.55).

The 12-volt power lead should be switched power, meaning it's live only with the ignition switch on. Ground, as its name implies, grounds to the body. We suggest making a mini-harness to support ...