3rd brake light won't work. Replace bulb...nothing

Warranty. That Jeep should still be under warranty.

First things first: check the fuses and bulbs. After that, have a look at the brake light switch which located at the brake pedal. These switches are known to fail from time to time, and are relatively easy to replace. Pay attention to installation instructions for calibrating the switch triggering position as it has a simple but necessary setup procedure.

Check the brake control switch situated just above the break pedal arm under the dashboard. Could be a wire loose or unplugged or the switch itself could be faulty

Change the bulb End see if that works, If not there is probally a short,

Brake light switch. If I remember correctly, the third brake light works off a seperate circuit from the other brake lights so part of the switch could be bad.

The light assembly is grounded to the body through the mounting screws. It sounds as though it is a bad ground. You could run a ground wire to a bolt on the frame from a mounting screw to check for aground problem.

just follow the wires from the brake lights and you'll see the ground. its probably coroded

I think there are 2 fuses for those switches. Fuse #11 & #39

Hope that works for you

if the bulbs are good, the only thing left is the headlight switch, or wires. black/yellow wires from the switch all the way back to bulbs. ck power to the bulbs first. if no power, then ck power at switch.

check the fuse for the stoplights. Even though the 3rd one is working it should be on a different fuse. With both of them not working even after you changed the bulb it would seem to lead to a fuse.