Alright well I have a 1977 Ranchero. My brake lights decided to stop working! I think the wiring is weird, when I turn on the lights, the right turn signal indicator illuminates slightly. For a while I would get only my right brake light working, however the left turn signal worked fine (wth??). I looked and the tail lights work, just not the brake lights, checked fuses they are fine. Any ideas how to fix this?? Also, does anybody have a wiring diagram for this vehicle?

 

It sounds like you have a ground issue. I ran into the same problem on my 66. When i turned on the lights my turn sig light on the dash came on really dim. Go to each fixture and clean all the corrosion out of the sockets and make sure that there isn't any corrosion on the socket, the wires and anywhere around the lamp itself. The lights rely on a chassis ground in order for them to work properly. The reason why your turn sig light comes on dim is the taillight fixture is using it as a ground, its a poor ground and thats why its not working. Check the grounds, change the bulbs and you should be fine!

 

beside checking for grounds, might check the connector at the brake switch attached to brake pedal