There are small fusable links built into the wires that run from the battery to they junction block. These fuses blow and the only way to tell is to check continuity of the wires.
In the pic below the black cylinders in the wire run by the persons thumb, are the fusable links.Your wires may be a differant color, all depending on what year your car is.
Below is a wire diagram for an 86 fiero, showing the fusable links that may be bad.
------------------ ARCHIES JUNK IS FASTER THAN SHAUNNA'S JUNK 12.3 is faster than a 13.2