On my 99 f-250( work truck)the trailer lights dont work, well actually the running lights work but nothing else does. But when i hook it up to my 05 (personal truck) every thing works.... What could be the problem???????

 

Both trucks are outfitted with OEM 7 pin connectors? or is the 99 an aftermarket add on ect..Also, superduty's have seperate fuses in the BJB for turns/directionalsfor trailer functions..