Brake light out

[jdvier]

Doing the spring tune up and found that the right side brake/turn signal does not work. I was unable to get power at the socket. Is there a fuse that I do not know about? Was told by a local rv tech that it could be the fuse on the new (2013) F250. Checked the relays and they work ok.
Is there a way to trace the wires back without taking the bottom covering off?
Thanks in advance
Jack

[steves]

Did you check the power at your 7 pin connector? That would tell you if it is the trailer or the truck.

[BB_TX]

Go to this trailer wiring info page. Scroll down to the 7 pin connector information.
You can use a short wire to jumper from pin 4 (+12v) to pin 4 to see if your light comes on. That will tell whether it is the trailer or the truck.