Here's a picture of from my 05 SC, most 04 - 08 year models are probably the same.

 

Thanks for posting pics!

 

I guess Ford could have wired a socket in the bed for you to plug everything into, but since most trucks will never get a cap put on them that would be an unnecessary added expense that would overinflate the price of our trucks in materials, warranty, labor costs, etc. Bravo to Ford for keeping it simple.
And the reason for stopping the wire at the door or under the hood in later models is because some of us wire the camper shell for accessories that are only used on the camper shell. Instead of running wires all the way down the underside of the truck, mine enter at the front of the camper shell and are wired to the camper shell. When the camper shell gets removed, so do its wires. If Ford had run the wires all the way back, I would have had to run another wire back up to the front of the bed. This uses less wire and is much simpler than wiring back to the tailgate then up into the camper shell.
I think the more pertinent question is, why don't camper shell manufacturers wire their shells to accommodate all the installed lighting accessories?
Again the most obvious answer is so that we the consumers have options about how we want our toys wired.

 

Well most shells I have seen only have a dome light and 3rd brake light, both of which are generally at the back. My shell did come wired for them with a pigtail hanging in the back driver side corner of the shell. I ran my harness with brake, constant 12v and ground wires and installed a weather-pack connector to facilitate easy removal although I have yet to need to pull my shell off. I still think since Ford bothered to put the wire on the truck at all, they realize people will be using it. I would think they could go ahead and spend the extra dime per truck and stick it in the trailer light harness or something. I would suspect most people run it up the back, maybe some up the front but nobody runs it through the drivers door

 

Just because your cap has a dome in the back doesn't mean they are all like that. Some shells have a dome in the front.
Plus, some people want their camper dome on a switch in the cab and it's simpler to run the wires from the front to the back once, instead of from the back to the front for a switch then to the back again.

It's still easier to go from under the driver through the firewall to a switch then back out to wherever. Your way would cause me to waste 2X the bed length's worth of wire.
Ford agrees with me.

 

Well since that wire is only a brake light wire and not a dome light wire, I still contend it should be in the back since I'm pretty sure no cap manufacturer puts the brake light in the front

 

I've never seen a cap with a 3rd brake light that didn't also have a dome light. But then, I haven't seen every cap made.
So for someone wiring a dome light and a 3rd brake light, I still maintain that the wiring is simplified by going in through the front of the cap instead of the rear. You're going to be in there to tighten the clamps anyway, so I've found that's the most convenient way to route all the cap wiring as opposed to a hot wire in front and the brake wire in back.

It is a good thing in my opinion for Ford to continue to do it how they are doing it. At least that wire is easily accessible and it allows both of us to route the wiring however we want it. Freedom is a good thing, and you are free to disagree.

 

Okay, so found the infamous "green wire", wired 16ga back to the cap and have tried all 4 wires on the cap and still no 3rd brake light... any help, something I'm missing??? Thanks

 

So when you say you "tried all 4 wires on the cap", You mean you just powered up each one by one? Have you ran a ground to the brake light as well? My shell only had 3 wires because the grounds for the brake light and dome light were tied together in the shell but I could see that some would have 4 if the grounds were separate.

 

I noticed someone said it was illegal not to have the 3rd brake light. I have mine wired but I wired it so it only goes on when I press on the brakes and when I think the lights are on. Is that what its supposed to be like? Or am I mis understanding it?

D

 

How else would you want to wire a "brake" light? Just sayin

And yes they can ticket you for not having it functional.