No brake lights?

How would I check this? All my brake light fuses work, but my brake lights still will not work. I know the voltage under pedal should be 12, but I am not sure how to check to see if this is the problem.

Left brake light is not working. Have replaced bulb and circuit board. Tail light and turn signal work fine. PLEASE HELP

1998 C1500 5.0. My brake lights have recently stopped working on my truck. Both of the brake lights in the tail lights would not work and one of the two lights on the cab brake light was not working. It turned out to be a bad buld in the cab light so they are fine now but the tail lights still are not working. I can hear the relay working properly, the parking, reverse, and turn signals are fine just the brakes. When the brakes are pressed it is getting about 12.5 volts to the socket (between the positive and the ground in the socket) but still no lights. I can visibly see the bulb is fine but even tried it with others just in case and still nothing. The ground seems to be fine, the power seems to be there, this makes no sense to me anyone have any ideas?

*After checking many different scenarios I found that the socket is getting 12v when the bulbs are out of both lights but if I put a bulb in either light it will not read any voltage at either light. Does anyone know what would cause this?

Have you resolved this issue (I see it's been almost 2 months since your post)? I have the same truck, and the same issue with my right rear turn signal. Same symptoms. Bulb is fine, voltage is fine. I found that the di-electric grease (tan colored gunk inside the bulb socket) had dried up, turned a dark brown color, for whatever reason. I used a fine-tipped tool to scrape the old crud out of the socket, and sure enough the light once again worked like a charm. However, this only worked for about a month, and now the light works intermittently. I am going to replace that plastic socket assembly (the thing that holds all 3 bulbs) and see if that fixes it.

1998 Chevy Pickup, 165,000 miles. I have no brake lights, the third light up top works fine, as do all running lights, turn lights, back up. But no brake lights. I have replaced the brake switch( 2 of them, one was DOA out of box!), Brake relay under the hood, all bulbs. I have traced all wires all the way to the back, they are fine. I can take a wire that is 12v hot and touch it to the wires that go back and I get brake lights. Is there some part that makes the turn signal and brake power go together or is it done in the break switch? What other parts are in the system?

THANK YOU FOR YOUR TIME AND HELP !
George

Ok, I was thinking that my problem was somewhere in that area. Where could I find the turnsignal switch assembly at? Is that where the power 12v from brake light and signal come together? THANKS FOR YOUR HELP !