Any good diagrams for wiring in a seven pin trailer receptacle to a 1999 Ford F-150. Can’t find an unused plug in the back.

 

They make a kit that you just plug into the truck with the existing plugs. Your 99 should work just fine. I bought one and it didn't work on my 97 even though the kit was for a 97-03. I think my issue is that I have a 97 model truck that was built in mid 96. I think I got left-over 96 parts bin stuff.

 

Yea, RA carries Ford kits.

Not that you need it, but Google Image search has the diagrams.

 

Don't know if their still available but U Haul wiring diagrams for their trailer light kits were on their website at one time. It's got to be a fairly universal or generic diagram.

 

That plugs right in by the spare tire. Pricey, but no need for a 7 to 4-pin adapter.

Not sure how this forum takes to linking to helpful advice on other forums, but if you google that part number in the link, you’ll get advice on how the install works.