loughman

Does anyone know specifically where there might be a dedicated wire to tap into for the dome light and 3rd brake light when adding a fiberglass cap to the bed. The cap dealer said they just splice into a wire at the one of the tail lights, then somewhere above the headliner, but I read somewhere, Ford provided a dedicated wire...any help?? I'd rather use a dedicated wire if one exists to avoid a potential future problem....

BucketMan

If you can wait till tomorrow I should be able to get you an answer then.

I had a ARE put on my truck the other day with a 3rd brake light and a dome light. I'll see where they ran the wires tomorrow when I get a chance to crawl under it.

It is hot wired so the dome light can always be turned on though.

elrod64

When I had my are cap installed they used a dedicated wire under the hood on the drivers just in front of the firewall. There was a green wire there that the cap dealer said was the dedicated wire that they ran under the truck. I wasn't in the shop when they did it. I do know that they also removed the drivers taillight and tapped in there also- possibly for the brake light. I wasn't allowed in the shop for insurance reasons so I couldn't see exactly what they did.
Jim

BucketMan

Ok, I took a look, im no electrical genius, so bear with me.

For power they tapped into the bolt that connects the battery to the fuse block located at the front of the engine bay. There are 2 large red cables that connect the battery to it, these are secured with a small bolt and nut. They simply attached a wire to it with an inline fuse and then ran it around the engine compartment towards the back of the truck.

Now, this is where it get a little lost. The wire runs on the driver side and near the firewall there is another inline fuse. On one side of the wire a very small guage blue wire with orange stripe runs into a factory wiring harness. The harness is pretty substantial and taped up pretty well, I have no idea what it is for, the wire simply disappears into it. On the other end is a white wire that enters a piece of loom and goes with the wire from the power source to the back of the truck.

I hope its not too confusing, but, thats all I got!

murf

Yup, gotta run either from the fuse box or directly off the battery for the dome. If you run direct off the battery you have to put an Inline Fuse!! But yes it'll be constant power so make sure to turn it off. If your ok with leaving the keys in to run the dome you can run off the constant power coming off of you 7 pin harness. It's the orange wire.

stmartin84

Sorry to dig up an old thread, but I'm looking for help with this. Can anyone tell me what fuse I can tap into (maybe a spare?) to run the dome light and possibly add a couple more of the same line? I also want to add a couple 12V power points in the back as well as wire up the third break light. Thanks!

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/

Greg Owen

I have a matching Tuxedo Black Jason cap on mine. It was wired up where I bought it, but watched them do it. They removed the left tail lamp assembly and spliced the brake lamp & dome lamp in right there. The dome lamp is wired to the tail lights, so the tail lights have to be on for the dome lamp to operate.

On a side note, I also ran a continuous hot wire myself to the back, installed a couple of switches--one for 3 LED strips, and one for a 12v power supply. If you want, on your 7-pin plug, there is one wire that is "hot" while the truck is running. It is meant for while towing RV's to charge any 12v system they may have installed. You could tap that wire for your auxiliary 12v plugs, but would only work while vehicle is running.

Everything is connected with simple male & female spade connectors (coded, of course so there isn't any mix-up on what wires need to be connected to each other). When it comes time to remove the cap, I simply unplug everything and lift it off.

Pics below...

stmartin84

Thanks for the information first. To answer your question about "what am I going to power?" basically if we are sleeping back there we need a power source for charging cell phones, maybe an iPad and possibly blowing up an air mattress, but that's about it.

So, you're saying if I tap into the 7 pin the truck has to be on? I guess I could run a wire from the passenger side fuse panel using one of the spares and a 10A or a 15A fuse to a direct line to the new 12V plugs.

As to the third break light I can't tap into the 7 pin break lights?

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.