Trailer running lights

More than likely a blue or yellow mini fuse within the engine compartment fuse panel.This is awkwardly mounted partially under the brake lines leading to the mastercylinder. Remove the cover and look underneath for fuse labels. The original owners manual will also provide fuse layout descriptions.

I would check fuse 38 in D.E.Bishops link to fuse block.

Here are the standard wiring diagrams for plugs and sockets or vehicle and trailer if you will.

Wiring Diagrams

NOTE: There isn't any wire for running lights.
You wired your motorcycle trailer, pick the one you want to use. I believe it is standard to use the "Tail light circuit" to power the DOT Lights. With a Four Way hookup, the Tail Light circuit is the only circuit available.

Don't forget, the relays isolate the fuses(power) for your trailer from the vehicle light circuits.

Ford Fuse Block

You should have a fuse box under the hood somewhere around the master cylinder.
If you don’t find a bad fuse there go under the back of the coach and follow the the wire harness from the 7 way receptacle up the frame there should be another connection/plug. Pop that apart and check terminals inside also ford runs the wire harness very tight against the frame rail, make sure you don’t have any chaffed wires on that harness

Im sorry for the confusion. I have a 2006 Class C motorhome on a 2006 Ford E450 super duty chassis. At the back bumper of the motorhome there is a trailer hitch and a 7 pin connector. I was wondering if there is a fuse in the cab for trailer running lights so i can check it. From the 7 pin connector i am using a 7 to 4 pin adaptor to plug in the trailer light harness that i have used for aux lights on the motorcycle carrier

I haven't seen a trailer with a fuse in the brakes, blinkers, or backups. I've only seen them powered and fused by the TV. Then, I haven't seen all trailers.

I have seen TVs with and without a relay as KD4UPL said.

Still not sure of your statement "RV has running lights just none at the 7 way trailer plug". Sounds like you have a trailer plug "recepticle" on the back of your trailer to plug the carrier into.

If so and you have trailer running lights then it is a bad connection between the recepticle and the trailer lights. Trace that back to where it is connected to the trailer light wiring.

Since you said you wired it, I have to ask, did you use the carrier as a return path for the light grounds? I've seen that done, but the ground wire from the plug has to be grounded to the carrier frame also. I've always found it best to run a ground wire rather than use the frame.

I don't know where the fuse is but here's something to think on. I had a Dodge truck that had a relay at the rear. It was energized by the running lights on the truck and pulled power off the 12v charge line at the 7 pin to feed the trailer running lights. I'm certain it was factory.

Yep, checked everything at the plug, everything works but no running lights... The RV has running lights just none at the 7 way trailer plug

I assume you checked for voltage at the trucks plug, If there is 12v then poor grounds are very common.

Many are under the dash in fuse block on left fender well