I have a similar problem, my left breaklight goes out when i apply the breaks when my lights are ON. when they are off everything works fine. when they are on, when i put on the left blinker the right reverse light slightly blinks and when i apply the breaks the left taillight dims and switches power to the left reverse light. I see no grounds in the rear of the truck i checked all the grounds under the dash and hood i could see. Going to buy a break light switch form autozone soon, but if it isnt that i am lost. Any suggestions would help a lot thanks!

 

sounds to me like a short in the system, only way to find it is to start tracing wires with an ohm meter.

 

+1
that definitely sounds like a short. the brake and tail light wires are probably touching somewhere. Hopefully you'll get lucky and it'll be either in the light itself or close to it and not somewhere in the wiring harness

 

Look at the ground on that light. Also look at the trailer hitch connection for corrosion or water in the harness.

 

Im having trouble with my driver side brake light. I've changed the bulbs and afterward it would work, but then after 30 mins or so, it stopped working. So i fiddled with the brake light again and checked to make sure it worked and it would. The next day I took a look at it to make sure it was working properly and nouthin happen. Its not both sides that are not working just this one. Could it be the brake light switch causing this or the brake light wiring harness? If you can help assist me with this problem I will be more than happy.