Third brake light wasn't working at all, changed all four bulbs. I now have the cargo lights working, but no brake lights. Here's the kicker, with a tester I'm getting power to the brake light bulb holders. So with new bulbs, why no brake lights? I thought maybe bad ground, and by using my tester and making a new ground against the body it lights up my tester, but why would the cargo lights work than? All other lights are working

Thanks,
Ryan

 

The check the ground of the light harness, you will need to use the ground of the bulb socket for your test light. I have a feeling that will give you the answer.

Bypassing the ground to the body with the test light gives the idea that the sockets for the bulbs don't have a good ground.