99 f350 7.3 all lights working but running lights wont go off

 

Do you have an alarm or auto start in the truck? If not I'm thinking the headlight switch, if you wired something into that circuit it could be backfeeding, gauges, stuff like that, that is very uncommon. it's rather easy to pull the switch out, unplug the headlight switch and see if they go out. I dont think they run off a relay, so you have a bad switch or something is backfeeding power to the running light circuit.