OK, I’m stumped. The left and right brake lights quit working, but the turn signals work. The 3rd brake light worked for a while, now that’s quit too. The cruise has quit too. I changed the brake light switch, a monster 3 contact thing, but that didn’t help at all. Is there a trick to these? Someone told me chevy had brake light problems with these, but they didn’t tell me what the problem was…
The symptoms point to the brake light switch or its wiring. Is the switch properly adjusted? Is there power (or ground, depending on the way the circuit works) to the switch? You’re going to need a wiring diagram to further troubleshoot this.
Normally power is switched to the lights. I suggest you get something like a test light so you can check for power with. It looks like power isn’t getting to the switch for some reason.