I have an 06 F250, and I was redoing some horrible wiring by the PO on our horse trailer today.

I've been wanting to add some exterior lights on the trailer and run them to my upfitter switches. I have the 6-way plug in the bed. I added a black wire to the plug side (12v) and ran it up to the trailer for when I add lights, the wire is already there.

Now, on the truck side of this, what wire powers the 12v on the plug? How would I wire it to one of my upfitter switches? I've never known WHAT powers the 12v connection on the plug, as it can't be a constant, so.....what's it wired to exactly?

 

Do you have a DVOM (multimeter)?

 

I'm not very familiar with a 6 pin connector. The stock connector at the rear is 7 pin.

However, I'd assume that whoever put the 6 pin connector in the bed wired the 12V. It is powered through a relay when the key is on. According to your owner's manual, the battery charge circuit is fuse #107, through relay #301 in the Central Junction Box under the drivers side dash.

Normally when wiring interior lights in a trailer, a battery is put in the trailer to run the lights, and the battery is charged when the truck is running via the 12V wire.

 

Yea...I posted this question a little pre-maturely (when I came in for some water) I went out and checked it when I got it wired together and it's 11.87v with KOEO.

Ok, so now plan of action would be to run the 12v wire to a small battery, then wire the lights to the battery and put a switch on the trailer somewhere. Now....what sized wire to run from the plug to the battery? I'm assuming 16-18 ga is too small to charge a battery....

What kind of battery is recommended?

Do I need to put some kind of junction box by the battery?

 

From the plug to the battery you probably want about 10 gauge. That's generally what is on the truck side anyway. The type of battery probably depends on how much light and how long you want them on. They make small gell cell batteries that are used for trailer breakaway switches and can be used for lighting. I'm not sure where you'd get one though. Generally you'd use a deep cycle RV battery.

You just need to find a place to put it, and put in a battery box. Run a 10 gauge wire from the plug to the battery. Run a 10 gauge ground wire from the plug to the frame, then from the frame to the battery. Then you can wire your lights to the battery however you see fit.

 

Great info.

Few more questions.

The plug on the truck side is grounded, and the plug on the trailer side is grounded to the trailer (part of what I had to re-wire today, PO had trailer grounded through ball).

So, can I not just ground the battery to the trailer, and that's it?

Also, what's to keep the lights from putting a drain on the truck battery when the lights are on?

 

Yes, you can just ground the battery to the trailer.

The lights will not drain the battery on the truck unless the key is left on. When the key is off, the trailer battery charge relay switches off and disconnects the truck electrical system from the trailer.

 

Awesome, thanks!