Therefore, your car's battery "negative" terminal is connected to the metal framework of the car (some older cars - mostly foreign - utilized 'positive ground' systems but this is no longer done).
AUTO WIRING FOR DUMMIES PLUS
"Where is the power coming from and is there a path to ground?"įor practical purposes, the flow of electricity is now considered to be from positive (voltage, designated by a plus sign +) to negative (ground, designated by a minus sign - ).
It may do this through any number of connections and through other devices, but tracing the path is straightforward if you always ask the question: That is, the flow of electricity always runs from the source of current through the device and then to ground. Ready to go on? Okay, let's start with the fact that all cars run on Direct Current (DC) electrical systems, as opposed to alternating current (AC) which runs your home. STOP! DON'T READ ANY FURTHER UNTIL YOU REALLY UNDERSTAND ALL THE TERMS LISTED ABOVE! This in no way makes it more difficult to wire or troubleshoot all that's required is to remember that the system is the reverse of normal systems. Note: Some cars and trucks utilized "positive ground" electrical systems, where the positive lead from the battery connects to the frame and the negative lead goes to the electrical wiring harness. No electrons will flow - and therefore nothing will work - unless the circuit ends in a ground. Without a ground there is only a POTENTIAL circuit. In cars, the metal chassis is the ground (that's why the battery's negative lead is bolted to the engine or frame) and the power source is the positive lead on the battery. That is, electrons must flow from the power source through the device to a ground. Ground: All electrical devices must be part of a circuit. IMPORTANT FACT! This is the only formula you will ever really need to understand basic electricity, be it in your car or in your house. The wire diameter must be large enough to carry the current without heating up and melting off its insulation. Example: a 50-watt brake light, operating on 12 volts, will draw 4.1 amps (4.1 amps x 12 volts = 50 watts). Why is this important? Because designers of circuits need to know the amount of current required for a given device (such as a fan, horn, light, etc.) in order to figure out which diameter wire to use. Watts: The unit of power in electricity and the product of Amps x Volts. IMPORTANT FACT! High resistance is the cause of ALL electrical failures - with the exception of broken wires and lack of grounding - both of which will be discussed later. Corrosion, loose terminals and too-small diameter wires are three very, very common causes of resistance. The more current which flows through an area of high resistance, the hotter the wire will become, ultimately failing. The higher the resistance, the more current must flow to overcome it. The unit of resistance is called the OHM and you can think of it as a kink in that garden hose.
Resistance: This is a restriction to the movement of electrons through the wire or circuit. When you tighten the nozzle the water shoots out further and faster. Think of this as the speed of the water coming out of the garden hose. The greater the rate of movement through the wire, the greater the number of amps.
AUTO WIRING FOR DUMMIES MANUALS
All vehicles' manuals specify the system voltage.Ĭurrent: This is the movement of electrons in the wire, expressed in a unit called the Amp. Older cars run on six volt systems and newer (most 1956 and later) utilize twelve volt systems. If you think of your garden hose as the wire, the water pressure would be equivalent to the voltage. Voltage: This is the force (or pressure, if you like) of electricity in the wire. It's the movement of electrons which runs the devices which make our lives - and our cars - so comfortable and convenient. Think of these little guys as "bullets", traveling down the wire.
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