I have a 2004 Dodge Ram 3500 Dualy. All the lights work on the truck but when I plug in trailer lights I don't get Left turn or left brake lights on the trailer only. I disassembled the receptacle and traced the wire to the bulk head with no faults found other than no power to the what I think is the coresponding wire. I checked the fuse and it was good. I noticed that when I turned on the right turn signal I could here two flasher units clicking. One under the dash and one somewhere near the under hood fuse box. When I turned on the left turn signal I only heard the one under the dash. Soo my questions are. Is there a separate flasher unit for trailer hookups and if so where is it located? What is the Dodge wire color for trailer left turn( I think its yellow )? What would cause one side and not the other to work?

I believe thers a fuse in the fuse box u need to pull for it to work (undr hood)

There is not two flasher units, your hearing your relay clicking. While in your driveway raise your hood and try locating the click with the signals on. It sounds like a short in your wiring. (either the trailer or truck, more likely the trailer)
Good Luck
Mark