2003 F-250 diesel superduty PU

It could be your headlight switch as the dash lights andparking lightsgo to that, and there is a microprocessor inside the switch. But there are 3 or 4 other relays in the central junction box that are called trailer tow relays and they may be knocking the lights out as well. It could also be aloose or poor connection on one of the switches or relay not making contact.