I own a 1989 chevy pickup extended cab, and have been having trouble with my right side panel of lights in the back of the truck, I replaced the panel and it worked fine for about 2 months, now when I disassemble and disengage the pigtail connector it will work fine until I step on the brakes and everything shuts off except for the parking lights, I have no turn signal nor brake lights the left side is working fine, any help would be greatly appreciated! Thanks in advance!

Check your body grounds on that side. On my 84 silveraldo, I had the same thing but on both sides, that trubled me for weeks. After talking with friends they saggested a broke wire or ground. After cralling from one end to the other I found 1 loose grond wire, re-attached it then it all worked with out insodent. Don't get agrovated it will take time to trace it down. Hope this helpes.

Cjt has soom good points.
I have a friend that has a '97-'96 (cant remember) Z-71 with sort-of the same problems.
After cleaning/checking all connectors, turns out it was where the base of the bulb connects in the taillight housing itself...
Just a thought...