The electricity that flows in an automobile starts with the alternator. As the engine spins, a belt connected to a series of pulleys turns the alternator brushes, creating electric current. In older vehicles, this current is regulated with an external voltage regulator and connected to the alternator via wires. Today's vehicles are almost all internally regulated, meaning that if the regulator goes out, it is likely the entire alternator will need replacing. The regulator keeps the voltage from dipping and spiking and maintains 13 to 15 volts constantly so that the electrics work well.
The Wiring
The current created by the alternator is carried throughout the vehicle using a complicated set of wires. These wires carry the electricity to the accessories that are powered by the 12-volt electrical system. Some wires carry the current; some go to a ground point such as the vehicle's chassis. All electrical systems have positive and negative wiring so that it can complete a circuit. Each wire is covered in a rubber protective sheathing so that the current cannot ground to the chassis or any other metal part of the vehicle. If wires are noticed that have nicks or damage to the insulation, they should be replaced or repaired immediately to avoid possible fires or shorts.
The Fuses
The fuses protect the electrical system. They act as the weak link, sort of like the u-joint on a drive shaft. When the current exceeds a certain number of amps, the fuse pops, cutting electrical flow to that device completely. Because the fuse blows before the device does, money is saved and major problems are avoided. Never replace a fuse with one that has a lower or higher amperage rating. They are designed to let go at certain amperages for a reason; if you change the rating of the fuse, the device and the vehicle may not be protected correctly. It is a much better idea to figure out why the fuse is blowing than to up the limit of the fail point.
