Handbook 652 Body Electrical Diagnosis Over-current Protection Devices Fuses, circuit breakers, and fusible links are built into every automotive circuit to prevent damage from excessive current. Excessive current can be caused by a short to ground before a load. When the load is bypassed there is nothing to limit current in the circuit. Without a fuse in the circuit, wires and connectors could be damaged by high current flow. The circuits protected by a single fuse are designed so that normal current does not exceed 70% of the fuse ’ s rating. Technical Training 11