Re: Weird starter solenoid problem
The likelyhood of getting two brand new solenoids with the exact same problem is almost zero. I would guess it was an issue with the wiring because you switched from a three wire to a four wire.
On the four wire, one of the wires feeds 12 volts to the coil, bypassing the drop down resistor when the vehicle has one. My guess is that somehow you got voltage going into the actuating lead. That would cause it to stick "on."
To anyone with the same problem, try removing a battery lead while the starter is stuck on. Immediately replace that battery lead. If the starter stops spinning, it is what I speculated above. If the starter keeps spinning, the that isn't it.
If that happens, remove the wires from the small lead. If that stops the starter, there is voltage on that lead when there shouldn't be. If it keeps spinning with those wires removed, the solenoid is stuck on and it is what is defective.
Probably too much to test since it fixes it to replace the solenoid with a three wire one. This info is just for those who really want to know what caused the problem. Not at all practical, I just want to know for sure.