Electrical Joy

[Swerve-Driver]

1966 Chevy 283 3spd LWB HEI and corresponding alternator. Worked fine for ~6 years.

Earlier this summer I came into my garage to find that in the middle of the night, my truck crashed into my Camaro. Dang.
Examination revealed that for some reason the truck starter engaged in the middle of the night driving the truck into my car (spun the tire on the truck after it hit my car), then smoked the starter wiring harness, melting the small wires in half and stopping the signal to the starter. From what I can tell the truck was only driven by the starter. Engine did not start during this event. Thankfully, the damage was only to the vehicles. No crushed kids, no burnt garage, didn’t happen in a parking lot, etc….

Had the starter rebuilt, new battery and re-made the wiring harness (firewall to starter portion).
No blown fuses- before, during or after the accident.

The harness going to the starter has;
Wire that is always hot (Black)
Wire that is hot when the key is in the ‘run’ position (Red- formerly cloth covered resistor wire)
Wire that is hot when the key is in the ‘start’ position (Purple)
Wire for oil or temp sending unit. (Green)
I replaced the cloth covered resistor wire with standard stranded copper wire (Red).
I verified power to these wires with a trouble light.

When I turned the key to ‘Start’ position, the engine began turning over and attempted to start (hasn’t run since June) so I let the switch move to ‘Run’. The starter kept on going. Moved the key to ‘Off’ and it kept going. Jumped out and disconnected the battery. After re-checking everything, I tried again with same result.
Suspecting the key switch, I pulled it from the dash and removed it. I jumpered the ignition key harness connector and the engine began turning over and when I removed the jumper, the starter remained engaged and turning over. Had to disconnect the battery.

I tapped on the starter solenoid and the horn relay to see if that helped- no change.
I am out of ideas and not sure what to try next- any ideas?
Any input you guys might have is appreciated-
S-D