Junior AACA






Automobile Wiring Diagram

Parts of the Electrical System


The generator is a part that charges the battery of the vehicle. The battery is used to start the engine, run the lights, the radio and many other things.  The battery (like a flashlight battery) will run down and needs to be re-charged. The generator which is run by the fan belt which turns the generator and produces energy that is put back into the battery. Some cars the generator is connected to the engine by gears that turn the generator. The alternator replaced the generator and is what is on most newer vehicles performing the same function.


The coil is key part of the electrical system that takes the voltage from a battery (usually 6 or 12 volts) and passes it through a series of both thick and very thin wires. This process causes the voltage to increase to as much as 20,000 volts as it leaves the coil. That very high voltage is passed to the spark plugs to ignite the gasoline and air mixture in the combustion chamber of the engine. It is this firing of the gas in the chamber that pushes the piston in the chamber down giving the engine power


The starter does what the word implies it starts the engine. It is a motor that rotates the engine crankshaft that moves the pistons up as well as operating other parts of the engine. Once the engine is running on its own the starter stops and is not needed until the car needs to be started again. Compare the starter to pulling the cord on a lawnmower.

Stoplight Switch

This part is self-explainable. It is a switch that turns on the brake light (rear lights) on when the driver puts on the brake.  The this switch is either mechanically connected to the break peddle or hydraulically tied into the brake fluid system

Dimmer switch

The dimmer switch is used to turn headlights of the cars to the high beams or to the low beams. Low beams are used to drive when there is traffic. The high beam is used when the driver needs to see way out and when traffic is not coming at the car. Dimmer switches in the early cars where often on the dash board or steering wheel, then they were located in the 40s, thru the 70s on the floor and operated by the drivers foot, now may dimmer switches are located on the turn signal switch behind the steering wheel and operated from by the drivers hand.