Ok. I still have no brake lights and seem to have hit a wall. Starting at the fuse block, I replaced the fuse. Then I went to the brake switch and have power to the switch, switch is good, and power out of the switch. Replaced the turn signal switch and have power coming out. Pulled the sill plates and the wire harness is still in its original condition and still in the clips. To the trunk. I replaced all 4 sockets and tried running a different grounding wire from the socket to a screw in the trunk. Nothing. I have tail lights, marker lights, turn signals, and hazzards. I keep thinking if a wire was grounding out in the trunk, I would have more lights not working. I'm stumped, but there has to be something I'm missing!

Do you have +12v on the white wire in the turn signal switch when you activate the brake switch?

Hmm. I will try that. Wouldn’t it be ok since I installed a new turn signal switch? Do you mean at the harness?

In the trunk do you have 12 volts at the brake light sockets? All the sockets dead at the same time would indicate a main feed wire is dead. I would open the harness connectors and trace from where you have power and work back towards the rear. It is either a broken wire or a bad connector pin in one of the connectors. As a last resort you could run a dedicated brake light wire from where you do have power all the way back to the brake light splice in the trunk. At least you will have brake lights while you try and find the actual problem.

I have power to the sockets as tail lights. Is there another wire that supplies power to illuminate the second filament when the brakes are applied? I did not think so as there are only 2 wires per socket.

There are three wires going to the red taillights. (Plus a light green to the white backup lights that don't seem to be your issue.)
- Brown wire runs from the lights switch to all four red tail lights. That wire uses one of the two filaments - The brown is the +12V and the light's ground are that filament's connections.
- Dark green wire runs from the turn signal switch to the two right side tail lights. It applies +12V to second filaments of those right side bulbs. Again the socket ground completes the circuits.
- Yellow wire runs from the turn signal switch to the two left side tail lights. It applies +12V to second filaments of those left side bulbs. Again the socket ground completes the circuits.

The test I mentioned would verify the +12 from the actuated brake switch makes it to the new turn signal switch. (You had mentioned that all the other lights; turn signal, flasher, and lights were all working as was the switch so the only that white wire from the brake switch and turn signal switch had not been checked for continuity.

Perfect! Thanks!

According to the wiring diagram, is there a wire harness somewhere between the back seat and the trunk, or do the wires just run straight through? I have been doing some reading and I am seeing controversy. If I don’t have to take out the back seat to check wiring that would be great.

Mike, Just check those harness wires end to end (between the turn signal connector and at the plugs for the bulbs in the trunk. If they have continuity, then the full harness run is fine.

Ok.

As I recall, the emergency flashers use the same filament as the brake lights. Are the flashers working?

Yes.

If you look at the wiring diagrams posted, you will see that the hazard flasher uses the same wires as the brake lights. So if the flashers work then the wires are good all the way to the steering column. That leaves the stop lamp switch itself or the wires to and from it. I know the OP says they are fine but what else is left? It may even be that the stop lamp switch has been pushed too far away from the brake pedal. There is a round clip on the switch threads that secures the switch. It is adjustable and sometimes it slips letting the switch not make contact with the brake pedal.

Or something wrong with that new turn signal switch.

All good points. I hope it isn't the new turn signal switch. I will be taking all of this info and diving into it tonight after work. I hate electrical issues. I will be in touch.

An old mechanic's credo is when something doesn't work- go back and re-check the last thing you touched.

I may have missed it in the beginning of this thread, but generally there is a lot of times there’s an issue with grounding, whether it’s a wire or the sockets themselves. I’ve had that issue on a couple Firebirds.

I HAVE BRAKE LIGHTS! More importantly, I have all lights! Not sure what I did, but I started at the fuse block, checked over everything again, unplugged and replugged, cleaned up contacts, and there you go. I may have had a bad connection at the stop light switch because I replaced the original socket with crimp on blade connectors. Somewhere along the line I overlooked something, and on the second sweep I corrected it. Thanks for all the help guys!