I just bought a 03 f250 super cab recently and I'm trying to get all of the little things fixed. Noticed third brake lamp wasn't working so I unscrewed it and noticed it was unplugged. I plugged it back in and it stays on all the time. Also have noticed the radio lights stay on dim after vehicle is shut off and locked. What could cause this to happen? Been trying to trace it down but I'm not having any luck. Someone had put in a sound system prior to me buying it I guess and then took it out, nothing appears to be cut or spliced in that I can see. Any help is much appreciated!

 

Wow. Something is powering those lights. I would take a shot pulling fuses one at a time to see if one of them kills the lights. Just to get a direction to head. Also could be a ground issue somewhere causing power to find another ground path based on the radio lights staying on dim. Maybe unplug power to the radio and see what happens?
Not sure where the connection between the cab lights and third brake light would be.
Good luck.

 

Either a short or a fault in the VSM/GEM could cause this.

Do your door locks work?

 

Door locks work perfectly