Originally Posted by J Birder
As they come from the factory, trucks are wired to provide power for charging. However, it is not connected.
On a Chevy, you need to add a fuse in the fuse panel, On a Ford, you need to add a fuse and a relay in the fuse panel. The relay is usually stored in the glove box. I am not sure about how Dodge does it.
My old truck - 2004 GMC and my new truck - 2006 Dodge - BOTH already were hot on pin #4, but both have/had towing packages factory installed, not dealer installed.
Check pin #4 at the truck plug to see if it is hot, if not, look for the fuse/ relay mentioned already. If it is, then.....
Check the trailer, follow the wire from the truck connector, it may go to some sort of junction box. I have a box on the back side of the front trailer frame cross member (right behind the battery box). In there, I have a hot wire that goes to charge my trailers battery. The wires for the lights (running, left turn, right turn - turn lights double as brake - and ground) all are connected to another loom that goes to the rear of the trailer for the lights, and the axle brake wire - with a ground, go to the axles from here.
Having a toy hauler, it has rear loading lights above the ramp door - I located the wire for reverse/backup lights, connected it to the loom going to the back, located it at the rear and installed a relay to the loading lights to become backup lights for my trailer. I know some newer trailers already have them, but mine didn't come with them. Wire loom on my trailer is the 7 wire loom used on the plug. All the wires are in there, but I needed to connect the wires together between the 2 looms in the junction box.
It would be nice if you have the wire already and just need a jumper to complete the circuit. IF the 7 wire loom doesn't have a junction box, it CAN be carefully opened and the hot wire located for this use.