Fusible Links
Fusible links are pieces of wire specially designed to melt when excessive current is passed through them. They act in the same manner as a fuse does to protect electrical circuits. They have a special insulation which will withstand high temperature, but will increase in diameter and bubble when the wire has melted. The wire in a fusible link is generally four gauges smaller than the circuit it protects. Fusible links may be individual wires with connectors at each end or they may be incorporated into the insulated battery cable.
Fusible links are found in some charging systems, inserted in the chassis wiring at a junction block in the engine compartment and at a starter connection. Number and location of fusible links varies with vehicle and manufacturer.