I found a bag with a fuse and relay in it.

 

The relay says Hi-power on it??

 

Your dealer should have installed them when they prepped your truck. They are for your trailer tow package. I'm pretty sure it's the fuse and relay for the charge circuit in the 7-way plug.

 

Off another forum:

The bag marked with the part number AL3T-15A416-AA provides power to the trailer battery charge pin located on the 7-pin trailer plug. Install the relay into position 9 of the underhood fuse box located on top of the radiator. Install the fuse into position 21. The circuit has a capacity of 30A.

If you have a backup camera, you may find another plug in the glove box. This plug is used to cap the camera wiring connector in case you remove the tailgate.

 

thanks for the info guys

 

Yes, that's what it is.
Mine were installed at the factory, but usually they are found in the glove box.

 

I was curious also since mine is still in the glove box...thanks for the clarification.

 

Ha, found these in mine as well the first time I cleaned it out. I put them in the center console for this very reason because I figured they were something the dealer might have forgot to install. Thanks guys!

 

I just found out today trying to get ready for camping that these weren't installed. Tried using the new jack on my camper (no battery installed yet) and it would not operate. Started checking the plug etc. Looked under the hood and there was no fuse in the slot 21. Found a note online that another guy had this problem. The fuse and relay were missing. I then remembered find a small bag in the truck. Amazingly, I apparently wasn't changing the battery in my camper all this time.

 

fuse gose in 9 and relay goes in 21

 

Thanks! I just bought a 2013 F-150 Lariat and found these in the glove box along with "Rear Video Camera Protective Cap". I doubt I'll be needing these any time soon, but still good to know I have them.