I posted this in the towing section, but hope to have a little better luck here:

06 2500 CTD 4x4. My truck did not come with the 7-way tow harness. I purchased the harness from the dealer along with a Brake Controller and associated harness. The 7-way harness directions contain no words, only pictures; which makes me feel even more like an idiot for asking this question:

The 7-way harness contains 1 blue wire which splits from the harness and routes into the cab. What is this wire for and where do I connect it? I originally though this was intended for the brake controller, but the directions for the controller and the harness that plugs into my factory connector under the dash both contain 4 wires each and none of which mention the blue wire from the 7-way harness.

Brake Controller and under dash connector/harness:
Black --Battery--connects to White with red trace from harness
Red --Stop Light--connects to blue with white trace from harness
White --Ground--connects to dark green with black trace from harness
Blue -- Brake -- connects to light blue from harness

7-way Tow Harness:
Bulk head connector on bumper
splice into reverse lights (white with green trace)
Power at battery
Fuse block (supplied in harness)
Mystery blue wire that runs from the harness into the cab and connects to ?????

Thanks again for the help!!!! I used the search function, but came up empty.



Later,

Greg

 

TotallyRad gave you a link in the other thread with everything you need to know. I don't know of any way to connect a 7 pin into a 4 pin and expect that alone to work correctly with full functionality. Your 4 way does not have wires for trailer backup lights, brakes or uninterrupted power for trailer battery/interior lights etc.