headlights on 1999 ford f250 superduty truck 5.4 engine

It could the bulbs or the sockets. It could be what I like to call the "Christmas Tree Effect". This is where if one bulb goes out, it sends the whole system haywire. Although, that is more than likely not the case with your truck. If you don't keep it clean or let it sit for a while in a field, you could get mice or other rodents that will eat the electrical,and since the wires for the headlights are upfront and in the open, they are an easy target; they tend to go for that first.

i have checked all the wires i didnt see any evidence of what you are talking about