Headlights come on with parking lights--Why?
 

My headlights come on when I turn on the passenger side parking lights.
Driver side functions normally. All bulbs are correct, battery and alternator are new, fuses are new, and I can't find any shorts(except under the bed!)

I'm ready for the experts to weigh in.

Thanks in advance.

My first guess would the headlight switch - it's making contact for the headlights when it shouldn't be. Unfortunately, the only way to find out is to get another switch and replace the old one.