When I bought my jeep it came with an aftermarket hitch and wiring with a connector installed... I hooked up a trailer and noticed that ONLY my left brake light, left turning indicator, and right turning indicator work. My Right brake light does not work at all. I grabbed my 12v current tester and poked a few wires while they were active right at the end where they meet the connector to see if they worked and I got the same results again with no luck on the right brake light, I pulled the right brake light out and poked into the wires there too and it seems that I get current there, I can't figure out the problem, anyone know a solution??

 

bad or wrong bulb.

 

The trailer converter box could be bad as well. It should be located behind the plastic panel that is behind your spare tire. Open that area up and make sure the connections are good and nothing is shorted/melted.

 

The bulbs are fine, I just replaced my left brake light/running light bulb today however because the running filament was burned out....

And thank you G_P I think we may have the culprit. I haven't checked there at all yet! I'll have to take a look when i get off work tomorrow. My guess is something is corroded because my grandfather (who i bought my xj from) had the hitch and wiring installed sometime back in 1994-1996 so it's had plenty of time to have corroded connections.

 

+1 on the converter box. I had one go out after only 2 years of use. I was convinced it was the trailer wiring until I checked it out.

 

Converter box, use a test light at the plus, ground the test light at the ground on plusg, the yellow is left, green is right, brown is running light. Brakes are both green and yellow.