Breakers And Fuses
A circuit breaker is a safety device that's designed to protect an electrical apparatus from damage caused by overload or short circuit. You're probably most familiar with circuit breakers from the electrical panel in your home. Unlike a fuse, which operates once and then has to be replaced, a circuit breaker can be reset (either manually or automatically) to resume normal operation.
A fuse performs the same task as a breaker but is much smaller and must be replaced after it trips. The conductor inside the fuse is made of a metal similar to solder. It has a lower melting point than the wire itself. The size of the conductor is calibrated very carefully so that when the rated current is reached, enough heat is generated to melt the conductor and break the circuit. A blown fuse must be replaced with a fuse of the same amperage. If you've got a fuse that keeps blowing, find the problem. Installing a higher-amp fuse and hoping for the best can cause significant damage or fire. Nearly all aftermarket harnesses use modern spade fuses instead of the old glass tube style.
Fusible links are used in some harnesses, as well. Much like a fuse, fusible links are short lengths of wire designed to melt at a certain current rating. They are commonly used instead of an inline fuse in main power leads to prevent current spikes from damaging the fuse block or harness.
 You don't need an array of...  You don't need an array of specialty tools to install a wiring harness. Some wire strippers, a crimping tool, and maybe a test light are typically all you'll require beyond basic handtools and drills. |
 Most wiring kits come with...  Most wiring kits come with insulated ring terminals and butt connectors (top). We tend to prefer un-insulated versions (middle), which, when used with heat shrink tubing, make clean, finished connections (bottom). Soldering connections is another option. |