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Ford Wiring System - Automotive Electricity 101
Understanding How Your Ford's Electrical System Works Is Easier Than You Think
Electricity has been doing our work for more than 100 years thanks to the efforts of inquiring minds who have paved the way for us. Thomas Edison, for example, understood that resistance to the flow of electricity created heat, and with enough current flow, light.In time, he learned if the filament were placed in a perfect vacuum void of oxygen, it would glow brightly without burning up. The electric light was born.
The electric light, however, is only a small part of what electricity does in our classic Fords. Electrical systems channel electricity to work for us. Think of your Ford's electrical system like an interstate highway system for busy electrons. In any electrical system, there are conductors, which carry electricity, and insulators, which don't. Insulators vary in resistance value, just like conductors. We want great resistance to the flow of electricity with an insulator just like we want low resistance in our conductor.
Copper and aluminum are typical conductors in automotive electrical systems. If extraordinary conductionof electricity is required, rare metals-like silver, gold, and platinum-make even better conductors than copper and aluminum. Copper and aluminum are the norm because they're more affordable and will work in just about any application. Automotive electrical systems use a combination of aluminum and copper depending on the application and function. Most of the time, you're going to see copper wiring.
The flow of electricity through copper or aluminum wiring is controlled by how much electricity you're trying to move and how much resistance there is to flow. Resistance creates heat regardless of how much electricity you're moving. When you flip on a heater or drop a piece of bread into the toaster, the heating elements in your toaster or heater create impedance or resistance to the flow of electricity, which makes them red-hot
Resistance is important in just about anything you do with an automotive electrical system. A wire that's too small for the load yields resistance and heat.
What Is Electricity?
Electricity operates much like thermodynamics. Heat energy (mole-cules in motion) travels toward a colder medium (molecules in slower motion). An excess of electrons will flow toward an area having a shortage of electrons. This flow of electrons is known as electric current.
Electric motors, for example, function from the flow of electric current through windings. The electrification of these windings creates a magnetic field or fields. As you know from high-school physics, magnets attract or repel. That attraction or repulsion, through electrification, runs the rotor or armature in a circle to create rotary motion around an axis. When we energize an electric motor, we're creating a circular magnetic field where a motor virtually chases itself in a circle. The whirring we hear is the continuous attraction of magnetic fields, which runs the armature in a circle. A generator or alternator uses a similar idea to get electricity in motion via the rotary creation of magnetic fields. In this instance, we move electrons instead of them moving us.
So How Does It Work?
Electric current flow through conductors is how we make electricity work for us. We start and stop the flow of electric current through the use of switches or variable resistors. Switches are electric-current traffic cops. When we close a switch, we make contact and complete a circuit (green light), allowing the flow of electricity. When we open the circuit and break the contact (red light), the flow of electricity stops. A variable resistor, as its name implies, varies the flow of electric current. When we have a lot of resistance, we slow down the flow of electricity. When we reduce resistance, increasing current flow, we allow more current to flow. Variable resistors exist in many forms. A dimmer switch is a variable resistor-like we find with a headlight switch or radio volume control. We vary current flow to control brightness, motor speed, and a host of other things.
Learning how to fix electrical problems is only a matter of knowing how electricity flows through a Ford's electrical system. There's no magic here, only the controlled routing of electrons. Electricity begins with the storage battery at the positive post.It flows through the system and back to the negative post, which is grounded to the car body and chassis, hence the term "negative ground." Your Ford's engine block, body, and chassis are an important part of the electrical system because they channel electricity back to the battery's negative post.
Power from the battery's positive terminal flows to either the fuse box or ignition switch first, depending on destination. Then, it flows to the switch, accessory, or lamp where it travels to negative ground. Power for lighting comes via a switch or variable resistor. Lighting circuit protection comes via a fuse or circuit breaker. Because headlights are high-current-draw safety devices, they are protected by a circuit breaker in the headlight switch instead of a fuse to keep the lights working in the event of a short circuit. The circuit breaker cycles headlights off and on so we can see the road and bring our Ford to a safe stop before getting help. Circuit breakers also cycle headlights off and on when switch contacts become corroded and resistance to the flow of electricity becomes high-creating heat at the breaker.