This one has me stumped. It must have to do with an electrical configuration. As the title says, plus I've tested with another motor out of the door and another switch on both the main and secondary switches.
What I have found is that.. given the two wires are supposed to switch polarity from 12v to about 0, which is what the switch accomplishes.. on the up stroke, both of the leads stay positive. But it can't be the switches, because I've swapped both of them with known good ones. Before swapping I did clean the old one, the contacts had a good amount of black electrical corrosion, as did the motor. Any ideas? I can't see how one of the wires is stopped from being reversed. Also given that both wires are 0v at rest. And that I can't isolate either switch for testing. Is there another component that may be faulty along the way? Besides a grounded wire, which is hard to see how one could increase voltage, and there is very little corrosion on the car.