Ground Wire to my Engine?

It's a reversing motor, uses the same voltage and ground. The switch reverses voltage and ground to the window motor. you use jumper wires to the motor, off the battery, for voltage and ground to motor terminals, the motor turns one way, reverse the leads, the motor should turn the other way. that's how I understand it. It doesn't take much to lower the window, more load going up. Just my opinion. good luck