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Symbols are used to represent various automotive electrical components. These are referred to as schematic symbols, and are used extensively in automotive service manuals to aid in diagnosing electrical problems. Although there are many electrical symbols used in circuit diagrams, we will look at some of the more common symbols.
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Current is the flow of electrons in a circuit. Current is measured in units known as amperes or amps (A). An amp expresses how many electrons are moving through a circuit each second. The more electrons moving through a circuit, the higher the amperage.
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A free, on line study of Basic Electricity/Electronics leading to a better understanding of Automotive Electrical/Electronic systems.
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A circuit is a path for electrical current. Current flows from a power source, traveling through the entire circuit and returning to the power source. Just like on a closed race circuit, the cars start at the starting/finish line, travel around the circuit (whether circular or road course) and eventually return to the start/finish line. If there is a break in the circuit, the current cannot flow.
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The automobile uses two primary methods to produce electricity: chemical, such as the lead acid battery, and electromagnetic induction, such as a generator. The battery, composed of lead plates immersed in a solution of sulfuric acid, produces voltage through chemical action. The generator, wheel speed sensor, and vehicle speed sensor all produce voltage through electromagnetic induction.
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Describes the chemical reaction that takes place during the discharging of an automotive lead-acid battery. How the molecules of the chemicals recombine.
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Exercise in calculating the current and resistance in parallel circuit branches.
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Circuit breaker are used in circuits that are susceptable to routine overload (i.e. power seats)or that are safety related (i.e. headlights). Most automotive circuit breakers are "cycling", meaning they reset automatically.
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All electrical circuits need to be protected from overload, which can result in a fire. An overloaded circuit is one in which the current exceeds the capacity of the wiring.
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To protect against spikes and surges, Clamping Diodes are connected in parallel with the coil. (see Fig. 4-20). While voltage is applied to the circuit, the diode is reverse biased and doesn't conduct the current. When voltage is removed and the induced current is flowing, the diode is forward biased and does conduct the current. This limits the current flow to a circular path through the diode and coil until it dissipates.
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Electrons move along a path called a conductor. They move by traveling from atom to atom. Materials that make it easy for electrons to move through them are called good conductors. Examples of good conductors include aluminum, copper, silver, platinum and gold. A material is a good conductor if it has many free electrons, or electrons that can be easily removed from the atom's outer orbit.
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The metal piece attached to the end of a wire is called a terminal. Although terminals are sometimes referred to as connectors, it's more accurate to think of a terminal as part of a wire, rather than part of a connector.
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The jumping off point for this self-study training. Lists each of the sessions in Part-1 of this course on Automotive Electrical/Electronics
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The simplest semiconductor device is the diode. It is made of one layer of P-type material and one of N-type material. Diodes allow current flow in one direction only. They act like a check-valve for current flow.
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Detailed description of the typical digital multimeter liquid crystal display including the varous annunciators.
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Detailed description of the rotary selector positions on a typical digital multimeter.
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Detailed description of the special features found on many quality digital multimeters.
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An automotive generator converts mechanical energy into electrical energy. This lightweight, high-performance machine generates electricity through electromagnetic induction. The generator is driven by means of a belt connected to the engine crankshaft pulley.
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Glossary of Automotive Electrical Terminology
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Like any other diode, Light Emitting Diodes or LED's allow current to flow in one direction only. The difference is that when forward bias voltage is applied to an LED, the LED radiates light.
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My self-study training courses will help you to understand the basic principles of electricity and how electricity is used in the automobile. You will also be given easy to understand diagnostic tips/principles.
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Electricity can be produced by magnetic induction. Magnetic induction occurs when a conductor is moved through magnetic flux lines, or when magnetic flux lines are moved across a conductor. A difference of potential is established between the ends of the conductor, and a voltage is induced. This voltage only exists as long as the conductor or magnetic field is in motion.
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Magnetism provides a link between mechanical energy and electricity. By use of magnetism, an automotive generator converts mechanical energy to electrical energy.
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Measuring current with the multimeter is not as simple as measuring voltage. You will need to THINK about what you are doing to avoid blowing a fuse, or damaging the meter.
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Measuring resistance and continuity is another common use of the digital multimeter. It too is a simple procedure, but there are a couple of important facts you must understand if you want to get accurate readings.
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Probably the most common use of the digital multimeter will be to measure voltage; however, it is important to understand the correct procedure for making resistance and current measurements as well. This will ensure that you will not damage the circuit you are testing or the meter itself.
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In order to make it easier to deal with large numbers, and very small numbers, the metric system is used. In addition to these large and small numbers being cumbersome, digital multi-meter displays are not large enough to display any number longer than 4 or 5 digits. The metric system is based on the number 10, making it possible to change the unit by moving the decimal point left or right.
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Ohm's Law states that current flow in a circuit is directly proportional to circuit voltage and inversely proportional to circuit resistance. This means that current flow in a circuit depends on how much voltage or resistance there is in a circuit. Since most automotive circuits operate on a 12-volt source, the amount of current is determined by how much resistance there is in a circuit.
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How to solve for unknown values of voltage, ameperage or resistance using ohm's law
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An open is a break in the path resulting in an interruption to the current flow in that path. Opens can occur anywhere in a circuit and are usually the result of loose, or extremely dirty or corroded terminals. Poor electrical connections are the most common cause of opens.
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The most common use of a rectifier in today's automobile is in the generator. The generator produces alternating current (AC), and for that reason is sometimes called an alternator. Because the automotive electrical systems use direct current (DC), the AC must be converted to DC. This process accomplished by a rectifier inside the generator so that DC is available at its output terminal.
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A relay is an electromagnetically operated switch. It is used to enable a low current circuit to control a high current circuit. The first relay ever used was to control current for the starter motor. Prior to that, the starter motor was engaged by depressing a large, heavy duty switch mounted on the floorboard. When the starter switch was moved to the instrument panel, it needed to be much smaller, therefore unable to switch the high current needed to run the starter. The starter relay enables the low current switch on the instrument panel to control a switch within the relay which is capable of handling the high starter current.
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Resistance is the opposition to the movement of electrons, or current flow. Resistance is measured in units called ohms. Most resistance sources are designed into the circuit and are referred to as loads, such as light bulbs or motors. All electrical devices, including wires have some resistance. A certain amount of resistance is required for any circuit, but excessive resistance will have an adverse affect on the circuit operation.
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One of the most common applications for resistors in the automobile has been the Heater/Air Conditioning Blower Resistor assembly.
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One common type of resistor that is used on circuit boards is the carbon-composition resistor (Fig. 3-1). The rating of this type resistor can be determined by the bands of color on it. The bands should be closer to one end of the resistor than the other. The end with the color bands should be on your left as you read them.
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Because of the heat created as a resistor resists current flow, each resistor has a specific wattage rating. Too much heat buildup will change a resistor so that its tolerance will no longer be in the designed range.
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This next application for fixed resistors is a little more complicated. It is the steering wheel radio controls. Figure 3-10 shows the diagram of the controls located on the left spoke of the steering wheel. This arrangement is referred to as a "resistor ladder".
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Earlier, we learned that some elements, such as copper, are good conductors, while other elements are poor conductors, but good insulators. There are still other elements, however, that are neither good conductors nor good insulators. If an element falls into this group, but can be chemically changed into a useful conductor, it is called a semiconductor. Silicon and germanium are the most commonly used elements for semiconductors.
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semiconductors can be made into good conductors by a process known as doping. Doping is the addition of impurities. The impurities affect how many free electrons the semiconductor has. Depending on which impurity is added, the resulting material will have either an excess of free electrons or a shortage of free electrons.
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As the name would imply, a series-parallel circuit is a circuit that combines a series and parallel circuit. Some of the loads are wired in series, but there are also loads wired in parallel.
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Using Ohm's law to calculate values in a series parallel circuit. Also give example using the lamp dimming circuit in the automobile.
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A short to ground occurs when current flow reaches ground before it is intended. This usually happens when a wire insulation is compromised allowing the bare wire to touch a ground. Since the metal body parts of the vehicle provide the ground path for most of the circuits, all the wire has to do is touch any metal part. The effect of the short to ground depends on the design of the circuit and on its location in relation to the circuit control and load.
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A short to power occurs when one circuit is shorted to the voltage of another circuit. Such a short can also occur between two separate branches of the same circuit. The cause is usually broken or damaged wire insulation.
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A solenoid is an electromagnetic device that is used to perform some mechanical work. Like the relay we just discussed, it utilizes a coil, that when energized, creates a magnetic field. The difference is that instead of closing a switch, the solenoid moves a plunger.
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Tool store specializing in automotive electrical testing and service tools
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Sometimes an electric motor runs too slow, or a lamp is dim, or a starter barely cranks the engine. These symptoms most often due to high resistance in the circuit. High resistance slows the current to a level too low for proper operation of a particular circuit.
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One of the most valuable tools that you will need to successfully diagnose and repair an electrical problem is the wiring diagram. This is your "road map" of the electrical systems. A good electrical technician will always begin the diagnostic process by consulting a wiring diagram.
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The kinds of resistors we have discussed so far are fixed resistors. This means their resistance value cannot be adjusted. Other resistors are variable. Their resistance can be changed by either mechanical control or by temperature change.
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We have said that a number of electrons gathered in one place constitutes an electrical charge. This charge is known as electrical potential or electromotive force (EMF). The unit of measurement for EMF is volt. It is this force that moves electrons through a circuit.
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Describes electrical charges and electrical potential (voltage). These are the invisible forces of electrical energy.
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Many wires are bound together in groups with one or more common connectors on each end. These groups are called wire harnesses. A harness usually contains wires from different circuits and systems.
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Wires are the conductors for electrical circuits. Most wires are made up of several smaller wires that are wrapped together and covered by a common insulating sheath. These types of wires are referred to as stranded wires.
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A Zener diode is a special kind of diode that is heavily doped during manfacture. This results in a high number of free electrons and electron holes. These additional current carriers permit reverse current flow when a specific reverse bias voltage is reached.
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