I am having trouble getting the factory wiring to work for my pickup box trailer. (91 ford f-250)
I have searched and found the wiring diagram for the truck and it shows orange w/blue stripe = right turn and brake
lt green w/orange stripe = left turn and brake
Brown = Tail lights
Black or grey = ground

I bought a new 4 prong plug for the trailer and wired it as it shows

White = ground
brown = tail lights
Yellow = left turn
green= right turn

I have checked all connections and double checked all colors are correct.

here are the symptoms i have

turn lights on get brake lights on the trailer
push brake and lights go off.
turn on either blinker and they both blink at same time but very dim
turn on hazards and nothing works

does anybody have any ideas this has me puzzled.

Also my other trailer with 4-prong works perfect so i have eliminated it being something in the truck

 

http://www.airplanesathome.com/FTEpics/BrakeCircuit.gif

 

Well, that's the correct color code for a 4-wire connector...
I'd check that the truck matches that code. It probably does since the other trailer works, though someone could've mis-wired that, and wired the truck to match...
Assuming that the truck wiring is correct, it must be in the wiring in the new pick-up box trailer. I'd see if there is any previous wiring work on that.

 

I pulled all the wires out of the trailer and found a broken wire. fixed that and all works like it should