I am sorry, but I am confused. Brake lights should come on when you press the brake pedal. I believe that your checking indicated that the switch is closing and supplying power to the wires in the trunk. Is this true? The brakelight circuit is working properly right before it feeds the individual brake lights? If your answer is yes then the problem is in the tail light assembly; bad connection, bad bulb holder, etc.

The fact that the third brake light in the rear window is working means you do not have to worry that it might be the bulb out sensor relay. When they are responsible for no brake lights none of the brake lights work.

So is your current issue with brake lights or tail lights? The tail lights should illuminate when the headlights are on or when the headlight switch is moved from off to the first position. Again check the wires for power before they attach to the tail lights with the switch in the appropriate position to light the tail lights.

Randy