CovKid wrote: So, the only wire you need (if you leave resistors where they are, is the solid yellow (flat-out) one. Thats positive and should go to motor-positive on controller. Ignore yellow/black.
Just a quick word of caution if you do use the stock wiring for this and you leave the resistors in place. You'll be feeding the output of the PWM controller to the motor via the yellow wire. The yellow/black and white wires will still be connected to this yellow wire, via the resistors. So make sure that the switch terminals on the yellow/black and white wires are properly insulated and tied up out of the way. Perhaps leave them inside the original switch housing and tape that somewhere securely.
I hate those resistors. If there was ever a barbaric way to reduce voltage - that must be one of the worst ways to do it. Even Joe Lucas himself would wince at that arrangement now.