Brake lights not working properly

Okay. Take a look at this wiring diagram. More then likely this is the switch but your vehicle is equipped with a combination flasher. So I would just go ahead and replace the flasher as they are cheap and easy.

Here is the info on this. Let us know what happens. Thanks

Okay. We are going to have to test the wiring at this point. I suspect you have a loose connection or high resistance in the wiring for the side that is dim. So looking at the wiring diagram, we need to measure resistance on each of the wires going to these bulbs and then the switch. The way to measure resistance, is you need to unhook the connectors at both ends of the circuit and measure the ohms of the wire. It should be less then a half ohm on a wire. I suspect you will find a wire that has more then that which will be the issue.

Dim lights means the bulb is not getting the full voltage which means something else is draining the voltage. In this case it is most likely a loose ground or corroded wire.

Let me know if you have questions and we can go from there. Thanks