The electrical circuits of a vehicle are protected by a combination of fuses, circuit breakers, and fusible links. These protective devices are located in the fuse-relay panel in the engine compartment. Each fuse is designed to protect a specific circuit, and the fuse panel itself identifies the various circuits. There are different sizes of fuses, including small, medium, and large, all with the same blade terminal design. While medium and large fuses can be removed with fingers, small fuses require pliers or a small plastic fuse-puller tool. When an electrical component fails, it is important to check the fuse first. This can be done using a test light to check for power at the exposed terminal tips of each fuse. If power is present on one side but not the other, the fuse is blown. Blown fuses can also be visually inspected. It is crucial to replace blown fuses with the correct type, as fuses of different ratings may be physically interchangeable but should not be used. The amperage value of each fuse is molded into the top of the fuse body. If a replacement fuse immediately fails, it is necessary to isolate and correct the cause of the problem, which is often a short circuit in the wiring caused by a broken or deteriorated wire. In addition to fuses, some circuits are protected by fusible links. These links are used in circuits that are not typically fused, such as those between the battery and the alternator or in the circuit to the starter or underhood electrical center. Fusible links are short lengths of heavy wire marked as such on the outer cover. To replace a fusible link, the negative battery cable must be disconnected, and the damaged link can be cut out of the wire behind the connector. The insulation is then stripped back, and the exposed wire strands are spread apart, pushed together, and twisted in place. The wires are soldered together using rosin core solder, and electrical tape is used to cover the soldered joint. Finally, the negative battery cable is reconnected, and the circuit is tested for proper operation.
