Ford Repair: parking lights ,panel and brake lights, ford ranger xlt, rear lamps

Question
i have a 1993 ford ranger xlt when i turn the head lights on .i lose he panel and parking lights but i can slide the switch in a little and they start working. i also noticed the  brake lights dont work when the lights are off but when you turn the lights on and get the panel and parking lights to work the brake lights will work. i have changed the light switch 3 times (2 from napa 1 from ford) what do i do know?  

Answer
Sounds like a possible ground circuit problem. Usually something like a bad light socket will cause the power circuit to find another ground, which may be what is happening with the brake lights. Since the only common item to the brakes and other lights is the rear lamps, I would start there.