Sorry i don't have a good wiring diagram all I have is the Haynes manual. You can remove the whole headlight switch assembly pretty easily and then you will have to trace those wires to where they go and see if that locates the problem. It will be a big PITA to lay on your back and trace the circuits out. The last heater blower motor I did also fried some wires. I didn't disconnect the battery while I was pushing the dash back into place and I must have pinched some wires or something as I got some smoke. Everything was okay though.
Your headlight switch itself could be bad. you could take the switch out disconnect the wires and jumper them together to see if you get the same symptom.