Basic knowledge of automotive circuits

carKey words of circuit basic knowledge: circuit rules 1. The composition of the whole vehicle circuit The whole vehicle circuit usually includes power supply circuit, starting circuit, ignition circuit, lighting and light signal device circuit, instrument information system circuit, auxiliary device circuit and electronic control system circuit composition. 1. The power supply circuit is also called the charging circuit.Accumulator,DynamoCircuits composed of, regulators and charging indicating devices, electric energy distribution (distribution) and circuit protection devices can also be included in this circuit. 2. The starting circuit is made up ofstarter,startRelay,startswitchAnd the circuit composed of starting protection circuit. The device for starting preheating under low temperature conditions and its control circuit can also be included in this circuit. 3. The ignition circuit is a circuit unique to gasoline engine cars.It consists ofIgnition coils,Distributor, Electronic ignition controller,Spark plugandIgnition Switchcomposition. The electronic ignition control system controlled by the microcomputer is generally included in the engine electronic control system. 4. The circuit of lighting and light signal device is composed ofHeadlamp,Fog lights, Marker lights,Turn signal, Brake lights, reversing lights, interior lights, and related control relays and switches. 5. The circuit of the instrument information system is composed of the instrument and itssensor, A circuit composed of various alarm indicators and controllers. 6. The auxiliary device circuit is a circuit composed of various electrical devices set up to improve the safety and comfort of the vehicle. The types of auxiliary electrical devices vary with different models. The higher the car's grade, the more complete the auxiliary electrical devices. Generally include windshield wiper and cleaning device, windshield defrosting (anti-fog) device, air-conditioning device, audio device, etc.The higher-level models are also equipped with electric window lifting devices, electric control door locks, electricSeatAdjusting device and electric remote controlrearview mirrorWait.Electronic controlairbagIncluded in the electronic control system. 7. The electronic control system circuit mainly includes the engine control system (including the control of fuel injection, ignition, emission, etc.), automatictransmissionAnd constant speed driving control system, anti-lock braking system, airbag control system and other circuits. Two, three kinds of circuit diagrams 1. Wiring diagram Wiring diagrams are wired according to the general position of the car's electrical appliances on the body. Its characteristics are: the number of electrical appliances (ie electrical equipment) in the entire vehicle is obvious and accurate, the direction of the wires is clear, there is a beginning and an end, it is easy to track the line, and it is more convenient to find.It pressWire harnessCompile and assign the wires to each wire harness to strictly match the position of each plug-in unit. In the vicinity of each switch, a table shows the connection and gear control relationship of the switch, the connection relationship between the fuse and the wire, and the color and cross-sectional area of ​​the wire. Disadvantages of wiring diagrams: the wires on the diagram are crisscrossed, the printed layout is small, it is difficult to distinguish, the layout is too large, and the printing is restricted; reading and drawing are time-consuming and laborious, and it is not easy to grasp the key and difficult points of the circuit; it is not easy to express the internal structure and working principle of the circuit . 2. Schematic diagram ◇ Schematic diagram of the whole vehicle circuit: For the needs of production and teaching, it is often necessary to find the beginning and the end of a certain circuit as soon as possible in order to determine the route of failure analysis. When analysing the cause of the failure, it should not be limited to a certain part in isolation, but the position of this part of the circuit in the entire vehicle circuit and the connection with the relevant circuit should be expressed. The advantages of the whole car circuit diagram are: (1) There is a complete concept of the whole car circuit. It is not only a complete whole car circuit diagram, but also an interconnected partial circuit diagram. The key and difficult points are prominent, and the complexity is appropriate. (2) The concept of high and low potential is established on this diagram: its negative pole “-” is grounded (commonly known as grounding), and the potential is the lowest, which can be represented by the bottom line in the figure; the positive pole “+” has the highest potential, and the most The upper line indicates. The direction of the current is basically from top to bottom, the path is: power supply positive "+" → switch → electrical appliances → ground → power supply negative "-". (3) It is possible to reduce the twists and turns of the wires, the layout is reasonable, the drawing is simple and clear, and the graphic symbols take into account the appearance and internal structure of the components, which are convenient for readers to associate, analyze, and are easy to read and draw. (4) The local circuits (or subsystems) are connected in parallel with each other and the relationship is clear. The connection points between the generator and the battery and between the subsystems should be kept in place as much as possible. The connections of fuses, switches and meters are basically the same as The original picture is consistent. ◇ Partial circuit schematic diagram: In order to clarify the internal structure of automobile electrical appliances, the relationship between the various components, and understand the working principle of a certain partial circuit, a certain partial circuit that needs to be studied is often extracted from the whole vehicle circuit diagram, refer to For other detailed information, if necessary, based on field surveying and mapping, inspection and test records, the key parts will be enlarged, drawn and explained. This kind of circuit diagram uses less electrical appliances and small format, looks simple and clear, easy to read and draw; its disadvantage is that only part of the circuit can be understood. Figure 8-7 shows the schematic circuit diagram of the Poussin engine. 3. Wiring harness diagram The wiring harness diagram of the whole vehicle circuit is often used for the connection, maintenance and wiring of the assembly line of the automobile factory and the repair shop. The wiring harness diagram mainly shows the connection parts of the electrical appliances in the wiring harness, the markings of the terminals, the wire ends,Connector(Connector) Shape and position, etc., it is the car circuit diagram that people can actually touch in the car. This kind of diagram generally does not describe the wire direction inside the wire harness in detail, only the wire heads and connectors exposed outside the wire harness are numbered or marked with letters in detail. It is a circuit manifestation that highlights assembly marks, which is very convenient for installation, wiring, inspection and maintenance. If the line ends of this figure are marked with serial numbers and colors accurately and used in combination with circuit schematics and wiring diagrams, it will play a greater role and receive better results. 3. The wiring rules of general automobile circuits. Automobile circuits generally adopt single-wire system, with electrical equipment in parallel, negative grounding, and the circuits are distinguished by color and numbering. The whole car circuit is divided into several main lines with the ignition switch as the center, namely: Battery live wire (line 30), accessory live wire (Acc line), key switch live wire (line 15). (1) Battery live wire (B line or No. 30 wire) Lead through the fuse box from the positive electrode of the battery, and also connect the battery live wire of the car to the starter live wire terminal, and then draw a thinner live wire from there. (2) Ignition indicator light wire (IG wire or No. 15 wire) The wire that has electricity only when the ignition switch is ON (working) and ST (starting), must haveCar keyTo be connectedIgnition system, Pre-magnetization, instrument system, indicator light, signal system, important circuit of electronic control system. (3) Dedicated line (Acc line or 15A line) is used for electrical appliances that need to be connected when the engine is not working, such as a retractor, a cigarette lighter, etc. The ignition switch is set to a single gear for power supply, but the radio and the like still need to work at the same time as the ignition instrument indicator when the engine is running, so the contact structure of the ignition switch knife and the contact needs to be specially designed. (4) Start control line (ST line or No. 50 line) The control switch (contact plate) of the main circuit of the starter is usually turned on and off by a magnetic switch. The attracting coil and holding coil of the magnetic switch can be controlled by the starting gear of the ignition switch. The attracting and holding coil current of the high-power starter is also very large (up to 40~80A), and it is easy to ablate the "30-50" contact pair of the ignition switch. A starter relay must be installed separately (such as Dongfeng, Jiefang and Mitsubishi Heavy vehicle). For cars equipped with automatic transmissions, in order to ensure neutral start, a neutral switch is often placed in series on the 50th line. (5) Grounding wire (ground wire or No. 31 wire) In the automobile circuit, the wiring method that uses the component and the metal part of the body (frame) as a common wire is called single-wire system, and the part where the body and the electrical appliance are connected is called single-wire system. For grounding or grounding. The grounding points are distributed all over the car. Due to the connection of different metals (such as iron, copper and aluminum, lead and iron), the electrode potential difference is formed. Thin sheet metal parts may cause poor grounding, such as the light does not turn on, the meter does not work, and the horn does not sound. It is necessary to pay equal attention to the grounding part and the live wire connection. Therefore, Hyundai Motor adopts a two-wire system in some parts, with special public grounding contacts, and special grounding circuit diagrams, which can be parallel with the fuse circuit outline diagram. In order to reduce the line contact voltage drop when starting, the battery pole pile chuck, the frame and the engine body are all connected with a large cross-sectional area of ​​the ground wire, and the contact parts are thoroughly derusted, painted, and tightened. Fourth, the general points of reading circuit diagrams (1) Looking at the "whole car", focusing on the "partial"-from "centralized" to "dispersed". The whole vehicle circuit is generally composed of various partial circuits, which express the connection and control relationship between the various partial circuits. To separate the partial circuits from the general drawing of the whole car, it is necessary to master the basic conditions and wiring rules of each unit circuit. The basic characteristics of the car circuit are: single-wire system, negative pole grounding, and electrical appliances in parallel with each other. Each unit (partial) circuit, such as power supply system, starting system, ignition system, lighting system, signal system, instrument system, etc., has some of its own characteristics. The circuit should be guided by its own characteristics to decompose and study the whole Car circuit, this will reduce blindness, and can read car circuit diagrams more quickly and accurately. At the beginning, you must read the legend several times carefully, check the approximate location and quantity of the electrical appliances on the car against the wiring diagram, the purpose of the electrical appliances, and whether there are novel and unique electrical appliances. If so, you should pay extra attention. (2) Grasp the function of the "switch"-the "object" under control. The switch is the key to control the on-off of the circuit. Pay special attention to the relay not only the control switch but also the controlled object. (3) Look for the "loop" of the current-the "path" of the controlled object. The circuit is the simplest electrical concept. Regardless of the electrical appliances, if they want to work normally (convert electrical energy into other forms of energy), they must form a path with the positive and negative poles of the power source (generator or storage battery). That is: starting from the positive pole of the power source → passing through the electrical appliances → returning to the negative pole of the same power source. This simple and important principle must be used no matter what circuit diagram is read, but it is often neglected when reading the car circuit, and can not figure it out. The car circuit diagram is based on the power supply and various electrical equipment of the car. The circuit connection relationship is connected by switches, wires, fuses and other power distribution equipment to form a complete circuit, and it is a graphic represented by a specific symbol. It can clearly show the working principle of each system and device of automobile electrical equipment and the internal connection relationship between each other. Learn to read the composition and basic expression methods of automobile circuit diagrams, grasp the working principle of automobile electrical systems, analyze the internal connections between automobile electrical systems, use electrical equipment correctly, and quickly analyze and eliminate the faults of automobile electrical systems. It is automobile inspection A basic skill that maintenance personnel must master. 1 The expression method of automobile circuit diagram With the rapid development of the automobile industry, the performance of automobiles is gradually improving, the types and quantities of automobile electrical appliances are increasing, and the structure is becoming more and more complicated. Correspondingly, the expression method of automotive circuit diagrams is also changing. The tendency of automobile circuit diagrams to be simplified and standardized is the general trend of the expression methods of automobile circuit diagrams in various countries in the world today. The basic expression methods of automobile circuit diagrams include circuit diagrams, schematic diagrams and electrical positioning diagrams. 1.1 Circuit diagram This is a traditional way of expressing automobile circuits. It is a circuit diagram that connects the actual positions of automobile electrical appliances on the automobile with wires from the power supply to the switch to the ground. The biggest feature of this kind of graphics lies in its similarity, which is specifically expressed as: the electrical layout in the figure is roughly similar to the layout on the car; the electrical appliances are represented by physical outline diagrams; the wire distribution is roughly the same as the actual direction on the car. This kind of graphics focuses on expressing the electrical appliances and wiring connections of the entire vehicle, and is not very helpful for reflecting the working principles of various electrical systems and analyzing the causes of failures. With the increasing complexity of automotive circuits, this type of circuit diagram has become less and less practical. At present, there are few such diagrams in imported models and domestically-produced imported models. 1.2 Schematic Diagram The schematic diagram is to reasonably connect each system component according to the circuit principle with concise graphic symbols, and then arrange the various systems. This type of diagram expresses the working principle of the car circuit and the interconnection control relationship. The key point is not to pay attention to the shape and position of electrical equipment and the actual direction of the wires. The circuit diagram is highly simplified, so that the circuit principle becomes concise, accurate and clear. It is useful for understanding the working principle of automotive electrical equipment and quickly analyzing and eliminating The failure of the electrical system is very advantageous. It is the most basic and practical information for analyzing the working principle of electrical systems and repairing electrical systems. What we usually say "reading car circuit diagrams" is mainly for this kind of circuit diagrams. Of course, this is also the need for technical personnel such as car inspection and maintenance. The place.The circuit schematic diagram can be further refined and classified as follows: car traditional (switch/relay) control circuit schematic diagram; automotive electronic control circuit schematic diagram; car switch internal position --- electrical connection diagram (ignition switch, combination switch, limit Inside of switches etc.TerminalElectrical connection is related to the operating relationship of electrical equipment and is very important for circuit state analysis); Block diagram of car circuit principle (it serves to illustrate the working principle of the circuit, but it is not specific enough). 1.3 The electrical appliance location map is used to indicate the specific location of each electrical appliance and its wires. Generally, it is drawn in the form of a plan view, a three-dimensional diagram or a physical photo, which can intuitively and clearly reflect the actual position of the electrical appliance on the car, which has high practical value. In some models, the positioning map can be further refined and classified: automotive electrical positioning map (determine the distribution of electrical components, connectors, junction boxes, grounding points, hinge points and diagnostic sockets, etc.); automotive wiring harness diagrams ( Determine the connection position of the wiring harness and each electrical appliance, the mark of the terminal, the shape and the position of the connector (Wire box, relay box) floor plan (used to determine the specific installation location of the fuse, relay, etc.). At present, most automobile manufacturing companies have adopted a combination of circuit schematic diagrams and location diagrams. In order to facilitate the combination of the two types of diagrams, the circuit diagrams of many models are also accompanied by a table indicating which location map the electrical appliances and wires on the circuit schematic diagram are on. 2 General essentials for reading automobile circuit diagrams The expression method of automobile circuit diagrams introduced above is only a simple summary of the expression methods of various current automobile circuit diagrams, and the induction methods in different textbooks are not the same. Due to the differences in the technical standards and text labeling of automobile circuit diagrams of various manufacturers in various countries, the drawing of circuit diagrams, expression of connection relations, representation symbols and text labels are not the same, especially for various imports. Some graphic symbols of automobiles (including domestically produced imported models) are still very inconsistent, and sometimes it is difficult to tell whether it is a wiring diagram, a schematic diagram or a wiring harness diagram. Although the drawing styles of different car circuit diagrams are different, which brings a lot of inconvenience to the reading, the basic working principles of the car electrical system are the same. Therefore, the reading of car circuit diagrams is not unruly or irregular, and still exists. Some general skills and experience can be followed. Master the method of reading the steam circuit diagram can generally start from the following aspects. 2.1 Fully prepare a. Remember as much as possible the graphic symbols used in the circuit diagrams of domestic and imported models (including wires, terminals and wire connection devices, contacts and switches, electrical components, meters, etc.)sensor, The meaning of some limited symbols of electrical equipment) and the meaning of the various signs, letters and other icons of the graphic symbols that indicate the direction of various wiring and wiring. This is the first thing you should understand to read and analyze the car circuit diagram, otherwise you will not be able to read the car circuit diagram, let alone analysis. Since the drawing of various car circuit diagrams is not standardized, especially some of the graphic symbols of various imported cars are still very inconsistent, you should carefully check the legends and graphic symbols, and be familiar with the names of the relevant components and their positions, quantities and connections in the diagram. Under the circumstances, avoid preconceived ideas, copy the old experience in the past, and pay attention to accumulating information to identify the differences in the circuit symbols of the same components of different models. E.g,resistanceComponents such as, switches, etc. may be expressed by different symbols in different models. b. To lay a solid foundation, you should start learning from basic knowledge such as electrical engineering and electronics (or automotive electrical engineering and electronics foundation). Should master DC, AC circuits, etc., this knowledge is indispensable for reading and analyzing traditional automobile circuit diagrams. For example, to understand the working principles of alternators and their regulators, starter control circuits, transistor ignition systems, etc., almost all of the above theoretical knowledge is required. For reading and analyzing the circuit diagrams of the electronic control system of modern automobiles, it is not enough to only master the above knowledge. You should have basic theoretical knowledge such as digital logic circuits and operational amplifiers. For example, some integrated circuit flashers use 555 timers, LED display panels use decoders, digital fuel meters use LM324 integrated circuit voltage comparators, and so on. c. Master the working principles of various components and unit circuits in the car circuit. This is the basis for reading various electrical systems and the entire car’s circuits. It must start with batteries, starters, generators and their regulators, relays, switches, and starting systems, power systems, ignition systems, lighting, instrument signals, and wipe and wash. System, air conditioner, radio, CD and other auxiliary equipment, electronic control system and other specific components or independent system are broken down and mastered one by one. d. Memorize the circuit marking symbols. In order to facilitate the drawing and reading of automobile circuit diagrams, many electrical devices or their terminals are given different marks. For example, the terminals of the AC generator connected to the live wire terminal of the power supply are indicated by "B" or "+", and the neutral point terminal. It is represented by "N"; "49", "L", "E", etc. are the basic signs of turn signal devices; "72" and "H" are the basic signs of electric horns and sound alarm devices; '30" indicates the normal fire line ; "15" means the live wire when the ignition switch is in normal operation; "31" means the ground wire, etc.It must be pointed out that in 1989, my country formulated the "Automotive Electrical Terminal Marking" based on the national conditions with reference to the German standard. This standard was replaced by the national automotive industry standard QC/T423-1999 in 1999. According to this standard,publicThe reading and analysis of car circuit diagrams will be of great help. . Proficiency in automotive professional English. Based on this, the meaning of the abbreviations on the wiring terminals in the circuit diagrams of some imported models can be quickly determined, which facilitates a comprehensive and quick understanding of the working principles of electrical appliances. This is also a difficult problem that plagues the majority of automobile maintenance personnel. Many textbooks and professional books have some abbreviations without clear explanations, which affect readers' recognition of pictures. 2.2 Mastering the method a. First easy and then difficult, gradually in-depth. You should start with familiar car models. For example, you can start reading and analyzing the circuit diagrams of some traditional cars such as EQ1090, CA1092, CA1110PK2L2, etc., and then read the circuit diagrams of Santana and Jetta models, and finally read Buick, The circuit diagrams of Passat, Accord and other models have been sorted and summarized from simple to complex in this way, and they have been improved, even by analogy. When I first read the circuit diagrams of modern cars, I will be confused about the pin names and functions of some ECUs and relays. At this time, you can temporarily bypass these contents related to the electronic control system and continue to read the whole car. For other electrical parts of the circuit, only after the data of these ECUs and relays are collected, can the current flow of each pin be sorted out, and people deeply understand the functional connection between the electronic control part and the traditional electrical part. This helps to increase our confidence in understanding car circuit diagrams. b. Break the whole into parts and make the complex into simple. For car circuit diagrams with only circuit diagrams, because the lines on the diagram are densely interlaced, it is easy to make reading and analysis errors. If possible, you can try to refer to relevant materials and objects to change the original car circuit diagram into different unit circuit schematic diagrams according to the system. . For the identification and analysis of the circuit diagram of the whole vehicle, it can also be divided into parts according to the above-mentioned method, and the whole image of the whole vehicle can be converted into a partial diagram of the system to facilitate the reading. The circuit diagram of each system unit can also be read by various methods. For example, the electronic control system circuit can be divided into the engine electronic control system, the automatic transmission electronic control system, the brake anti-lock electronic control system and other circuits; the engine electronic control system can be divided into fuel injection control, ignition control, emission control, etc. The circuit is read and analyzed one by one; at the same time, attention should be paid to the mutual relationship and mutual influence between the circuit of each system unit, so as to be integrated. c. Make a breakthrough and pass by analogy. When reading car circuit diagrams, we must understand a certain type of car circuit structure and its principles. Through this specific example, draw inferences and compare with each other to grasp some common laws of car circuit diagrams; then use these common characteristics as a guide to understand Other types of car circuits, so that you can find more commonality, by analogy; at the same time, you can also find the differences between various models. For example, if you master the characteristics of Jiefang brand car circuits, you can roughly understand the characteristics of a batch of domestic car circuits such as Dongfeng, Yuejin, etc.; if you master the circuits of Nissan, Mitsubishi, Toyota, etc., you can basically understand the characteristics of Japanese car circuits; The circuit of the Santana car can further understand the characteristics of the circuits of German Volkswagen such as Audi, Jetta, Polo, and Bora. Such repeated and continuous accumulation can obtain the ability to read various automotive circuit diagrams. d. Read the car circuit diagram according to the car series. At present, the number of domestic cars is increasing year by year, and brands are becoming more and more diverse. It is extremely unrealistic and unnecessary to read the car circuit diagrams of all types of cars. As mentioned above, as long as you break through one or two car models, you can learn by analogy. In order to cover a wider variety of car models with limited knowledge and energy, it is necessary to comply with Japanese, American, European (German, French), Korean and other car models. The system is divided reasonably, and one or two models are selected as the key objects to be mastered. Generally speaking, it is recommended to divide as follows: For Volkswagen, you can choose one of Santana, Jetta, and Audi; Toyota series as the representative of Japanese cars (Acco, Corolla, etc.); GM series as the representative of American cars (Saiou , Buick, etc.); Citroen series as the representative of the French car series (Fukang, Elysee, etc.);BenzThe car series and the Volkswagen car series belong to the same Germany, but they are a separate series, which are quite different and need to be mastered independently. 2.3 Several issues that need attention a. When reading partial circuit diagrams, you must first carefully read the legends. Finding out the type, quantity, and name of the electrical equipment included in this part of the circuit, and then summarizing the system to which it belongs, will help people understand the working principle of the circuit in combination with the commonality of the system. b. Familiar with electrical components and wiring. Mainly refers to the wiring connectors, junction boxes, relays, grounding points, etc. in the circuit indicating symbols, positions, connection methods, and internal circuits. These can be clarified by the positioning diagram, and the schematic diagram and positioning Cooperating with the reading of the diagram, it will be very helpful to analyze and read the car circuit diagram. It should be mentioned that the letter expression of the wiring color differs depending on the native language, so you need to pay attention when recognizing the picture. c. Pay attention to the status and representation of switches and relays. The state of the switch and relay changes, and the working state of the line also changes accordingly. We usually analyze the working principle of the circuit based on these different states. Such as the power supply of the ignition system, the ignition switch should be in ignition position (ON) or starting position (ST), etc. In the standard drawing circuit, the switch is always in the off state, and the contact of the relay is in the state where the magnetizing coil is not energized. The state of electronic switches such as transistors and thyristors depends on their specific conditions. For the relay, it is divided into two parts: the control circuit (power to the coil) and the main circuit (contact control circuit). In addition, in the electrical system, various relays also have multi-layer and multi-gear combination switches. When shown on the circuit diagram, there are two methods of centralized display and separate display. Pay attention to the difference when viewing the diagram. d. Use the loop principle correctly. The following mistakes should be avoided: one is to start from the positive pole of the power supply, and return to the positive pole of the power supply after passing through a number of electrical equipment; the other is to mix the two power sources of the battery and the generator, and start from the positive pole of one of the power sources and return to the electrical equipment after the electrical equipment. To the negative terminal of another power supply. e. Keep in mind the characteristics of automotive circuits: single-wire system; negative grounding; parallel connection of electrical equipment; low DC voltage; dual power supplies. f. Pay attention to the collection of data and the accumulation of experience. Due to the continuous emergence and application of new electrical equipment in automobiles, the circuit diagrams of automobiles have changed greatly. Therefore, you must be good at consulting relevant personnel for circuits that you cannot understand, and be good at searching and collecting relevant information, and pay attention to deep research on typical automobile circuits. , Pay special attention to the accumulation of actual work experience. g. About the reading method of the automobile electronic control system. Take the ECU of the electronic control system as the center; have a general impression of each pin of the ECU, figure out the rules of pin arrangement in several areas, and find out the power cord that supplies power to the ECU, and pay attention to the power supply of the ECU Generally there is more than one line. Find out the power supply status of each power line (whether it is a constant fire line or controlled by a switch); find out which grounding lines the system has, and pay attention to distinguish whether these grounding lines are inside the ECU or on the frame. Or on the assembly body; find out which are the signal input sensors of the system, whether each sensor needs power, and find out the corresponding power cord, where the sensor is grounded; find out which actuators are in the system, and Find out the power supply and the grounding situation, and the way the microcomputer controls the actuator (is it to control the grounding end or the power supply end). 3 Several typical styles of circuit diagrams The above-mentioned method of reading diagrams can be applied to any automotive circuit diagrams. At present, due to differences in national regulations and industry standards, the styles of circuit schematics drawn by various automobile manufacturing companies are different. The specific differences are mainly concentrated in the symbolic expression of the circuit diagram, the modularization of the entire vehicle circuit, the layout of circuit components, and the way of legends. And the way of expression of circuit status. The following typical style circuit diagrams are available. a. The abscissa type circuit diagram. Mainly based on the German Volkswagen car system. The circuit diagram of this mode uses number coordinates to mark the position of each line in the diagram at the bottom. The lines are arranged in parallel longitudinally, and each line is aligned with a number on the lower frame line. In the figure, it is generally not allowed to cross the line with a large span, and the horizontally connected line is represented by the "fracture marking method", that is, the line break is marked as the position number in the figure where the other section of the line connected to it is located. In addition to Volkswagen cars, Chery cars also use this method of circuit diagrams. b. Horizontal and vertical coordinate circuit diagram. The circuit diagram of this mode uses the horizontal and vertical coordinates to determine the position of the electrical appliance in the circuit diagram. For example, Mercedes-Benz uses numbers as the abscissa and letters as the ordinate to locate the circuit. c. Non-standard modular circuit diagram. Many car companies use this method of drawing, such as GM Buick, Honda, Dongfeng Citroen, Fukang, Toyota, Ford,BMW, Mitsubishi, etc. However, the specific circuit expression and graphic symbols of each company are different. When reading the diagram, please refer to the related circuit diagram and graphic symbol list. d. Mitchell circuit diagram.Has now become a Chinese regioncar repairOne of the main information. 4 Concluding Remarks Mastering the general essentials of reading automobile circuit diagrams cannot be completed overnight. We need to lay a solid foundation, familiarize with various components, lines, and terminal marks, and understand the expression methods and typical styles of automobile circuit diagrams. Take a scientific method of reading pictures and take the precautions in reading pictures seriously. From simple to complex, from easy to difficult, first understand the circuit diagrams of one or two typical car models, and by analogy, understand the circuit diagrams of one or two typical car models in different car series. Pay attention to the collection of data and the accumulation of experience, continuous practice and perseverance, in order to master the skill of reading automobile circuit diagrams comprehensively and proficiently.