Help us help you. By posting the year, make, model and engine near the beginning of your help request, followed by the symptoms (no start, high idle, misfire etc.) Along with any prevalent Diagnostic Trouble Codes, aka DTCs, other forum members will be able to help you get to a solution more quickly and easily!
Back story: Slant 6, electronic ignition. Ran great, but not charging. I was doing some testing, and ran the ignition side of the voltage regulator directly back to battery positive, not ignition + (start). Not sure if that was the right thing to do. It started charging at 13.1 volts. I revved the engine up and it spiked the voltage, and the truck died. I tried to restart it, no luck. I damaged something. That's when the troubleshooting started. Some things are checking out, however there are a few things I need help with.
With ignition in run position, 4/5 pin connector not plugged in at module, I get 12v on both inputs of ballist resistor, and 8v (run) and 12v (bypass) on output. Once I plug in the connector, the input values change for the run circuit. I get .5v on the input, and 3.5v on the output, which feeds the positive side of the coil. Is this correct? I ask because, when I ground the male pickup wire on the harness side, I get no spark. Thoughts? I can give all numbers for my findings, just not sure which are needed. Feel free to ask, and I appreciate the help.