2013 F150 crew cab. I hooked up horse trailer for first time and all lights work except for the interior lights and loading light in rear. Trailer dealer said I had a blown fuse (number 67) so I replaced it without any luck. Any suggestions?

 

Fuse 67 is for the parking lights/running lights. Do the running/parking lights work? The +12v to the trailer is F21 30 amp in battery junction box. Fuse is hot always but +12v then goes thru relay only in start or running position. Make sure you have a fuse F21 installed.
This is to charge trailer battery and can be used for aux. trailer lights if truck is running, otherwise you need trailer battery.


If you want trailer interior light or loading light to work you would need truck running or battery on trailer.

 

Relay number 9 was missing and fuse number 21. These were supposed to be installed when I bought truck!

 

Interesting, my horse trailer interior lights are tied to the running lights. It is a 2000 model though.