Originally Posted by Snowdog

For those examples you could tap into the 12v at the trailer hitch with no issues. If you were running something that pulls more than 10 amps then I would run a different wire to the outlets. If you are running up front to the fuse box I would use a 16 gauge power wire just to be safe. The lower the number of wire the thicker the wire is and the more current you can safely pull through it.

As far as the 3rd brake light goes, these trucks flash the same bulb as the brake light for their turn signal. That is the same as the trailer wiring. If you tapped into just one you would get a flashing 3rd brake light when that signal was active and possibly feed voltage into all lights and computer when the brake was applied with the turn signal on. There is a dedicated circuit for the brake light that is independent of the turn signals and that should be used. I just looked at my 13 XLT and it is very easy to find the blue/orange stripe wire to tap into. Get some wire loom and tie the new wire inside the loom to the existing harness running down the frame.

Also I always use wire loom when running anything. It looks neater and gives an extra layer of protection against shorts.

Originally Posted by stmartin84

In the spirit of being super clear I will do the following, please confirm.

for the 3rd brake light look for the blue/orange stripe wire and connect directly to that. No fues required? Run what size wire from this to the third brake light inside the wire loom?

For the 12V power plugs get 16 gauge wire (with a fuse?) and tap into the hot line of the 7 pin connector? What size wire should I use for this if it's under 10A? Then if I need more than 10A then go directly to the fuse panel with some 16 gauge wire and tap into any spare fuse with a spare fuse rated for higher than 10A?

Originally Posted by Snowdog

What are you going to run with the power outlets? That will determine how heavy of a wire and where you get your power from. If you aren't pulling a lot of power from the outlets you should also have a line running to constant power in there. Here is a diagram of that plug. You should be able to tap into the trailer wiring for the dome light in the cap, you can use the tail light wire (#4 vehicle end) if you don't mind the running lights on to have the dome light work or the constant 12v (#3 vehicle end).

Also check this page I found. It is for the 2011 but it also has a link to where the green/black wire is for the older model to tap into. Sadly there is not an easier way other than run a wire to the front of your truck. You could make a small circuit with a couple diodes and relay that tap into your brake lights at the rear or buy a module that does the same thing. It is a lot easier and cheaper to run a wire to the front. I would also make your connections with a butt connector and black tape to keep water out, personal opinion there.
https://www.f150forum.com/f38/2011-c...e-light-83548/

Originally Posted by mangwhop

I'm also stuck. Thought i would tap into the trailer hitch wiring but that causes 3rd light to flash with directional. I have an 05 f150. Also cant find that spare wire i keep reading about.