I have a 99 jimmy recently i noticed the left rear brake light works when it wants to any idea what might cause this? bulb has been replaced with new one.

 

*Moved to Lighting and electrical*
That being said, There could be a short, it could be a bad bulb socket, I would start with the bulb socket, since it is the easiest thing to replace, then if it still acts the same way, start tracing the wires to try and find a short.

 

Ill try the socket but i forgot to mention everything else works on that same bulb the hazards the turn signal.

 

so the running and brake function work? but the blinker and hazard does not?

 

No all the lights work just the left brake light only works off and on but i have found the problem its the wiper/signal switch one day i was in a parking lot and i was looking in the side mirror with the reflection of the car parked behind me i was checking if the brake was working and it wasn't so i moved the signal switch just slightly up and the brake light came on then i moved it down a bit and it went off again. Now my question is am i better off to replace with a new or used one? or is it just a loose connection and i can tighten it up?