[A1971Blazer]

there is no power going to the lights UNTIL you pull the switch on....so it won't blow a fuse if there is no current to it...the switch simply feeds power into the light circuit...again there is a dead short somewhere in the circuit.....probably a bare or burnt wire. you're gonna have to trace the wires to find it...
The brake lights and running lights are separate circuits....so the brake light circuit has nothing to do with the light circuit....it only operates the brake and signal lights.