Get a volt meter, only about $5 for what you need to do. Set it to a DC setting and ground the black leed. Then use the process of elimination with the blinkers/brakes/parking lights to figure out if its been shorted before it gets to the lamp. If you have 12V on when its supposed to be on, then the problems in his testicles I mean tezzas.

Then, once you've learned how to use a volt meter and done a little problem solving, install the stock lights because altezzas make baby jesus cry.