I have a 1996 Chevy Silverado c3500 Crew Cab. Brake lights and 3rd brake light do not work. The following do work: 1) running lights 2) turn signals 3) hazard flashers. I can hear the brake relay click when I depress the brake pedal. I have replaced the switch, relay. the fuse is good and my electric brake controller lights up. I am leaning toward a defective turn signal switch. I do have power at the stop fuse(20A).