My 1988 corvette conver. third brake light came on by itself and will not go out without unplugging the bulb. What can I do to correct this problem. Thanks for your help.  
  Jim  

Sounds like there's a short either in the brakelight swtich or in the wiring going to the third brakelight.  

Brake lights are actuated by a switch which is mounted on top of your brake pedal. When your foot is off the pedal the pedal is up and depresses the switch which opens the contact. Depress the pedal and switch closes turning on the light. With a third brake light, there might be a second switch that might have come loose and stays closed thereby 3rd brake light stays on but not the regular brake light. Check it out, adjust and tighten. That should do it!  

Thanks for the information. I will check these items and let you know what I find. I have had a back operation recently so it will have to wait for now, but as soon as possible I will find the problem. Your info gives me area to look in. Thanks again.
  Jimmy