[VetteVet]

Use the test light to see if you have power on the blue wire at the dimmer switch with the headlight switch on. If you don't then the headlight switch is bad or the blue wire is open to the dimmer switch. I would jump a wire from the red wire on the HL switch to the dimmer switch connector on the blue wire and see if the lights work.

HO455 is correct, the orange wire is the power feed wire for the tail lights, dash lights, and the dome light as well as the stop light switch.