This diagram shows the layout of a common car audio system and signal flow. The dotted black line shows the path of the preamp audio signal (before it’s amplified), from a head unit, through an equalizer and electronic crossover and to the amplifier. A video signal is also sent from the head unit to a pair of video screens in the back seat area. From the amplifier, an amplified audio signal (the solid black line) goes to each speaker in the system — one amplifier powers a subwoofer. The other amplifier powers a set of component speakers in the front of the car (with the signal first passing through the speakers’ passive crossovers) and a pair of coaxial speakers in the rear of the car. The gray line shows power flowing through a power cable (protected by an in-line fuse) from the car’s battery to the amplifiers.
A V-shaped or flat serpentine belt that’s driven by a crankshaft pulley and transmits kinetic energy to various accessories, such as the alternator, air conditioning compressor, fan, power-steering pump, and water pump.
The element in the air cleaner that removes impurities from the air. Most air filters are disposable, although some aftermarket types can be cleaned and reused.
An engine part that generates electric current that’s stored in the battery and used to start the car and run the electrical equipment.
A transmission that selects gears automatically, either by means of a hydraulic converter and a system of bands and clutches, or with an electronic transmission controller.
A box filled with a solution of water and acid called electrolyte. The box contains metal plates that store current generated by the alternator and deliver it to the parts of the car that operate electrically.
Devices that keep the engine warm in very cold weather when a vehicle isn’t used. These are especially important for starting diesel engines at extremely low temperatures.
In a vehicle with power brakes, a brake booster is located between the brake pedal and the master cylinder to increase the force applied to the pistons in the master cylinder.
The liquid used in the hydraulic brake system to stop or slow the car.
A system of hoses and metal tubes through which the brake fluid flows from the master cylinder to the brakes at each wheel.
A high-friction material that’s attached to the brake pad or brake shoe. When the pad is pressed against the disc, or the shoe is pressed against the brake drum, the lining grabs the disc or the inside of the drum, which slows the wheel and thus the car.
Curved pieces of metal on which are bonded high-friction brake linings that are forced against the brake drums to slow or stop the car.
A device that vaporizes fuel and mixes it with air in proper quantities to suit the varying needs of the engine. Carburetors have been replaced by fuel-injection systems on most vehicles built since 1990.
A pollution-control device that consumes unburned gas in the tailpipe and reduces nitrogen oxide emissions.
In a manual transmission, a device that disconnects the engine from the transmission to allow the driver to change gears and then allows the engine and transmission to resume contact and turn together at a new speed. In an automatic transmission, a clutch performs a similar function.
A rectangular box that contains the air filter. It performs the same function as the air cleaner.
A device used to check the amount of pressure created in a cylinder when the piston is at its highest point and is squeezing the fuel/air mixture into the smallest possible space.
An ethylene glycol or propylene glycol solution that raises the boiling point and lowers the freezing point of the water in the cooling system, prevents rust and corrosion, and lubricates the water pump.
A hollow, tube-shaped pipe in the engine block in which the piston rides up and down to compress the fuel/air mixture that drives the engine.
The part of the engine above the engine block that contains the combustion chambers and the valves. The spark plugs screw into the top or side of the cylinder head.
An engine that burns diesel fuel instead of gasoline.
Fuel for cars with diesel engines. It’s similar to home heating oil, kerosene, and jet fuel.
A metal stick that’s inserted into a reservoir to check the level of the fluid in the reservoir by means of markings on the stick. The most common dipsticks check the levels of engine oil, transmission fluid, and power-steering fluid.
Brakes that have calipers with high-friction brake pads, which grab a brake disc (sometimes called a rotor) attached to the wheel and force it to stop turning, thus stopping the car.
The part of the ignition system that distributes the proper amount of electrical voltage to each spark plug in the correct sequence. This task is now performed electronically on distributorless ignition systems.
A cap that over the distributor that has an outlet for each spark plug wire, plus an outlet where the wire from the ignition coil enters the cap to conduct high-voltage electrical current to the rotor.
The path of power from the engine to the drive wheels. Consists of the clutch, transmission, driveshaft, differential, and the axle on which the drive wheels are situated.
Brakes that use hydraulic pressure to force curved brake shoes against the inner walls of a hollow metal drum attached to each wheel.
The cast iron, aluminum, or ceramic block in which the cylinders and the crankshaft are located.
The most powerful computer onboard a modern vehicle, also called a powertrain control module (PCM). Controls most engine functions and processes signals from the various engine, emissions, and related sensors.
A device for measuring the distance, or gap, between two surfaces, such as between the center and side electrodes on a spark plug.
The sequence in which the cylinders fire on a particular engine to distribute the shock of combustion evenly and to reduce engine vibrations.
A device that removes impurities from the fuel before it gets to the fuel injection system. In fuel-injected cars, the filter is found either in the fuel line under the car, or mounted on the firewall.
A fuel system without a carburetor that employs an electronic fuel management system to deliver a specific amount of fuel to each combustion chamber in response to changes in engine speed and driving conditions.
Fuses protect the electrical components and wiring on your vehicle the same way they do in your home. They’re located in a fuse box (or boxes) that usually are found under or near the dashboard or under the hood.
The space between the spark plug electrodes. Adjusting this space is called gapping.
The seal between the cylinder head and the engine block. This gasket keeps the coolant out of the cylinders and free from contamination by exhaust gases.
An alternatively fueled vehicle that combines a small internal combustion engine and an electric motor to get maximum power with minimum emissions and maximum fuel economy.
An engine that works on power released by vaporized fuel and air burning inside the engine itself, rather than on an outside source of combustion as, for example, a steam engine does.
Cables used start a car with a dead battery by conducting current from another battery.
A vehicle transmission system in which gears are selected by the driver by means of a hand-operated gearshift and a foot-operated clutch.
A device that stores brake fluid and hydraulically forces it through the brake lines to the brakes when you step on the brake pedal.
A can-shaped device that screws onto the outside of the crankcase and cleans the oil as it circulates through a vehicle's lubrication system.
A brake system that uses a brake booster (or power booster) to make braking easier.
A device that uses hydraulic power to help the driver steer more easily.
A radiator cap on a coolant recovery system or radiator that allows the cooling system to operate under pressure at higher temperatures for greater efficiency.
A device that cools the liquid in the cooling system by allowing it to circulate through a series of water channels that are exposed to air ducts.
Devices located near each wheel to cut down the vertical bouncing of the passenger compartment on the springs after the wheels go over a bump or the vehicle stops short.
A device that delivers an electrical spark to an engine's combustion chamber, igniting the fuel/air mixture that produces the power that drives the engine.
The space between the center and side spark plug electrodes, across which the spark must jump to ignite the fuel/air mixture in the engine's combustion chamber.
A small electrical motor that causes the engine crankshaft to begin to turn, which starts the engine running and so starts the car.
A device that uses electrical current to start and engage the starter.
A device that keeps the hot coolant confined to the engine cooling passages to help the engine warm up more quickly. After the engine has warmed up, the thermostat allows the coolant to flow to the radiator, where it’s cooled and recirculated through the engine to prevent overheating.
A part of the clutch, activated by the clutch pedal, that allows the clutch to disengage. If you allow the car to idle in gear with the clutch pedal pressed instead of shifting to Neutral, you can wear out the throw-out bearing.
A thin oil that fills the automatic transmission so that it can run on hydraulic pressure. It’s also found in many power-steering pumps.
The process of replacing a vehickle's fuel filters, air filters, and spark plugs to ensure that air, fuel, and spark are available in good condition to obtain maximum engine efficiency.
A device that circulates liquid through the cooling system by pumping it from the engine water jackets to the radiator.
A device found on diesel vehicles that removes any water that may have contaminated the diesel fuel.
The inner and outer bearings found at each wheel that cushion the contact between the wheel and the spindle it sits on.