I'm setting up an appointment with uhual to get a brake controller installed on my 04 Disco. Is there anything I need to know before I go? I currently have the 7 and 4 way plug. I thought I read somewhere that it may already be prewired and just need to plug in the controller.

 

I wired my brake controller, and there was no pre-wiring in my '01 D2. IIRC, the controller required power with a circuit breaker inline and ground up front, one wire to the brake switch behind the brake pedal, and then one wire from the controller to the rear. You may check the owner's manual for the '04, but I doubt there is any pre-wiring. The wire to the rear goes to the brake contact in the 7-flat pins that are in the larger round trailer wiring connector, and I believe is purple in the 7 pin plug.

https://www.etrailer.com/faq-install...m-scratch.aspx

Wiring diagram at the bottom of the above link.