I used a toggle switch,there is a relay inside the actuator. At first I was confused and fried the original one. On my 97 I just grounded one of the wires at the 4x4 switch,but that truck originally had push button 4x4. On the Tahoe I connected the brown wire to key on positive,black to ground,and blue to toggle switch, key on positive . When the blue wire gets 12 volt positive it engages the front axle,disconnect the current and it will disengage. It works perfectly. Not sure what the other plug on the front differential is for,I guess for a light ?