I have a 200 E450 cutaway with a 7.3 PSD
I bought this vehicle recently.

When I first got the vehicle the tail, signal and body lights did not work. Fuses kept blowing in the trailer auxillary fuses under the hood. I traced the problem to poor wiring in the trailer. Once I disconnected the trailer and replaced the (3) 10 amp fuses under the Hood, I got everything working on the truck.

Next I rewired the trailer. Most everything now works (signals, hazards and brake lights) on the truck and trailer. But the tail and body lights do not work. They worked for a few seconds then went out. The tail and body lights don't even work when the truck is not plugged into the trailer. I swear I pulled every fuse under the hood, under the tailgatel and under the steering wheel and checked it 3 X. I even downloaded the fuse diagram from ford to for the E450 in an attempt to locate a fuse which may control this. I am still looking. I even changed a few fuses that were said to control the lighting just in case.However, I did not find a specific fuse reference for tail and body lights. The main bulbs appear to be good.

My next step will be to contact the Body manufacturer to see if they can help.
Thanks for any input.

 

Ford always used brown for the running lights on the main vehicle. And they are all on one circuit for the truck, and a seperate circuit for the trailering circuit. The trailering circuit may have a different color.

So, if the running lights work on the front, then the truck's circuit is good. I would try to find the wire for the running lights on the add-on body, disconnect it, and hook a little 12 volt battery charger to it to see if they light up. The battery charger has a circuit breaker that will protect it if you have a problem.