I have been trying to fix the tailer plug tail/park lights on a factory wired plug.
I now believe it is the relay, but my owners manual doesn't show a relay for this purpose. My Haynes manual wiring diagram shows a relay for tail/park lights. Anyone know where this relay should be. There are seven in the fuse box under the dash. Are there any others under the hood. I found 2 little boxes under the hood, next to the left front fender, with what might be 2 relays in each. Not sure how to take them out. Thanks for any help.

2003 Ford F250 7.3 Diesel

 

On the 03 Superduty, the trailer running/park lamp relay is integral to the Central Junction Box (fuse/relay panel rt side kick panel). It is not a serviceable replacement except by replacing the whole panel.

The alternative (if the relay has indeed failed) is to wire a generic relay around it to perform the same function.

There was a discussion a couple of months ago about this in which the owner did exactly that. Perhaps you can poke around and locate it. :edit: Here: https://www.ford-trucks.com/forums/7...ring-help.html

Also check fuse F38 in the same box. It supplies operating power for both the running and backup lamp circuits.

Steve

 

Thank You so much for the reply. Fuse 38 is working fine, and I am interested in checking the relay as you have described. I could run a jumper and make it work, But just thought I would try to fix it right. Just bought this truck and I am trying to learn a little about it. Thanks Jim

 

Don't know about the 03 but my 00 has another fuse panel under the hood and I have had to replace fuses in it going to the trailer harness. My ground wire to trailer had broken which then grounded only through the ball. Bouncing around created enough short to blow the fuse under the hood.

 

The 2003 SD is completely different and the 2000 component location and circuit information doesn't apply.

Steve

 

Thanks SHO89: I had figured that out. I printed out all the relay by pass info you mentioned, and will try to fix today, if it cools down a bit. I am in Ky and we have 90+ temps and 65/ 70 % humidity. Us fat boys sweat a lot. Thanks Hammer.