I have a 2007 F150 truck. I also have been pulling the horse trailer and the lights work until recently. Now it doesn't work and I bought a new RV and couldn't get the lights to work. I tested the brown/white wire and there is no juice. What should I do next please?

 

Start by checking the fuses...

 

Fuse, broken wire etc

 

All the fuses related to the trailer towing are good. Wires look good.

 

I replaced the R201 relay that is connected to the trailer tow parklights. There is still no juice on the brown/white wire. Another question, is it possible to bypass that wire to the brown wire that handles the truck parklights?

 

Is your problem with the trailer or the truck's running lights???

 

Problem solved. It was #10 (20A) fuse that was out. Weird, tho because I did checked all of the fuses 3 times. Don't know how I could have missed that #10. I do appreciate all of your suggestions and help. Thank you.