My friend has a 87 dodge ram and is having prob with the tail lights. He has brake lights untill he turns on the headlights or parking lights than he does not have brake lights. if you turn on the brake lights while running lights are on the tail lights will turn off all together. We changed the light bulb and still did nothing to help it. any ideas?

 

Sounds like something is shorting out. Could be a bad brake light switch on the brake pedal arm.

 

Definately a short, check wires and look for any breaks in the wires.