Ok, first of all, I'm new here so thanks for having me! I just picked up a 1996 Suburban 1500 that appears to have a factory reciever but has never been utilized. The wires in the rear end have never been touched. I found the connector to splice in the NAPA 4 pin and the taped up other 3 wires back there it appears Orange=12V, Blue=Brakes, White=???. I also located the Blue & Orange wires up in the engine compartment near the load center. Orange has a ring terminal which I assume connects to post A or B on the Aux. posts. Now I am stumped. Does the large Blue wire need to be redirected into the cabin to be the sending connection from my brake controller? This is on order at the moment and will be here next week. Additionally, what is the smaller gauge white wire at the rear harness? Thanks in advance for your help!