Looking for help. 86 Firebird 2.8... 3rd brake light doesnt come on but others do. the bulbs are fine cause when i put power straight to the wire going to the 3rd brake light.. all 4 bulbs come on. Can't find a decent wiring diagram for this. 3rd brake light is wired somehow in conjunction with the rear power hatch motor, and the way it's only powered when the hatch is closed, but i cant find where the wires going the lower brake lights connect to the wiring for the 3rd brake light. seems like they should all be wired to each other so when brake pedal is pressed.. they all light up. ?? Does anyone have any ideas ? or know where I can find a good wiring diagram..
Thanks very Much.

 

Nevermind......
I went back out and messed with it a bit and now all the brake lights work.. Not sure what the problem was.

 

Morning, I had this same issue. it turned out to be this weird gunk that was behind the bulb itself, almost like a clay or play dough substance. I would check and see if there is any of that on the connectors.

 

Thats old gm grease to keep corrosion away. It needs cleaned out and ne grease applied