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

 

The blue wire is the brake wire. I don't know for sure where you would tie it in to the original plug under the dash, but I'd just cut the blue wire on the brake controller harness and solder it on.

 

Splice it such that the blue wire from the 7-way, blue wire from the bulk head connector under the dash, and the blue wire from the controller all connect?

 

I don't know for sure where the light blue under the dash goes. I'd try to trace that out before I hooked power to it. I was thinking just cut the wire in the harness coming out of the brake controller. Splice the blue wire from your plug into the controller side and just tape up the other end that plugs into the under-dash harness. That way later on if you put the controller into a different vehicle or something you can just splice the 2 wires back together and don't have splices in your vehicle wiring.

 

Hopefully someone else with a 3rd gen that knows the wiring schematic will chime in here.

 

Gs, see if this helps a little.

http://www.etrailer.com/faq-wiring.aspx

 

since your truck didnt have the trailer wiring, does it even have the connector under the dash, and if it does, where does the blue wire from it even go?

 

It has the connector under the dash. I connected the blue wire from the dash connector to the blue wire on the Brake Controller.

 

Here's the factory wiring colors. I don't know if you've got it working but I thought I'd throw it out there in case.

7-way wire > Dodge Wire
Pin 1, Ground > #14 Black
Pin 2, Brakes > #14 Dark Gray
Pin 3, Tail Light > #18 Brown
Pin 4, +12V > #14 Red/Violet
Pin 5, Left Turn > #18 Yellow
Pin 6, Right Turn > #18 Light Gray
Pin 7, Aux > #18 White/Light Gray (Backup Light)

 

Don't know about 3rd gens, but a few of the 2nd gens I have worked on did not have the factory tow harness. On those trucks, sometimes the under dash brake controller connection was there and sometimes not. If it was there the blue wire extended out of the connector, through the firewall and down under the truck. Right under the feet of the driver, right at the "corner" between the firewall and floorpan there was a harness junction block. The blue wire would end at this junction block if the truck did not have the factory tow harness.

 

Thanks for the replies, but I still don't think I've found what I need. The 7-way harness plugs into the stock 4-pin at the bumper, splices into the reverse lights, connects to the battery, then has this mystery wire that goes into the cab:

 

The 4 way is the basics, stop, turn and tail. Additionally, in the 7 way you should use one wire for a ground to the battery and one to power the brakes from the brake controller. That gives you all the necessary wiring to operate your brakes, turn signals, stop lights and trailer brakes.

 

I have 4 wires coming off of the connector up under that dash that I connected to the Brake controller. Should this one from the 7-way replace one of those?

 

One of the wires from that connector, in the back of the brake controller, goes to the 7 way plug. That wire is the one that energizes the brakes.

 

If that mystery wire is connected to Pin #2 on the 7-way then it connects to the brake controller output. Which should be a blue wire.