In addition to fuses, the wiring harness incorporates fusible links to protect the wiring. Links are used rather than a fuse, in wiring circuits that are not normally fused, such as the ignition circuit.
Fusible links are sections of wire, with special insulation, designed to melt under electrical overload. There is usually one in the main wire from the battery, and near the alternator output side. If one melts, it must be replaced with a new link of the correct amperage rating. Never replace a melted link with ordinary wire; you run the risk of melting your entire wiring harness.
Fusible links are color coded red in the charging and load circuits to match the color of the circuits they protect. Each link is four gauges smaller than the cable it protects, and is marked on the insulation with the gauge size because the insulation makes it appear heavier than it really is.