Need help! I'm trying to convert my flat 4 prong plug to a 7 prong plug for electric trailer brakes. My 4 prong plugs into the 7 prong at the back of the truck. All lights work on the trailer. I found the wiring plug under the dash and connected the brake controller and it works. Under the truck behind the front driver side wheel well, I found the wiring plug that has the wires that go to the back of the truck for the lights and the 4 prong trailer plug. However, at this wiring plug the side of the plug coming from the engine compartment has two wires that stop at the plug. One wire is red and is always hot. The other is an off color with a black stripe and I can not get it to light up my tester no matter what I do. The red wire is connected to the power distribution box with a 40 amp fuse labeled "trailer". Is this the wire that should be extended to the 7 prong plug to power the electric trailer brakes? Is there anything I missed?

 

Grab the service manual for your truck from here. Wiring diagrams are in section 8W.

 

Thanks! More informative than Chilton.

 

Yeah, chilton really skimps on the wiring diagrams...... I suspect there is some legal issue with them printing them exactly though.

Definitely makes life easier.

 

Alright Guys with a circuit tester and some logic, I have it working! First, look under the dash for the blue connector (mine was white or just faded) and connect the break controller. I found the connector on top of the white square box (with every wire in the world going into it) to the right of the e-brake pedal.
Some people say that their ram does not have one, but they all do! It took me three days before I found it. It is hidden very well. Whether you have the tow package or not, the wire connectors are there.
Once you have the brake controller installed, look under the drivers side of the truck behind the wheel well and in front of the cab and you will find two wire connectors there. One connector will go from six wires to four wires. The four wires on the cab side of the connector goes to the tail lights and four prong trailer plug. The two larger wires in the center of the connector on the engine compartment side stops at the connector. The red wire is always hot and runs from the power distribution box through a fuse and trailer relay. The other connector has a blue wire that stops at the connector and this wire comes from the break controller.
Now take your circuit tester and check the red wire (should always be hot). Pull the fuse and check it again! Replace the fuse and check it again. Take the circuit tester and check the blue wire while someone pushes the brake controller override button or lever. The circuit tester light should go from being dim to bright!
Once you have these wires tracked down, all you have to do is extend them from the connectors up front to the seven prong plug at the back of the truck. The red wire (always hot) connects to the black wire on the plug (auxiliary power). The blue wire connects to the blue wire on the plug (electric brakes).
My electric trailer breaks work great now! At 50 mph I let up on the accelerator and pressed the break controller override button and the trailer breaks brought the truck to a smooth stop.
I hope this helps someone else!