Due to the different methods, drawing symbols, text labels, and technical standards of automotive circuit diagrams in various countries. The drawing methods of automobile circuit diagrams vary greatly from automobile manufacturers. Even the representation methods of automobile circuit diagrams of different companies in the same country are quite different, which brings a lot of trouble to the reading. It is very important to master the basic methods of reading automotive circuit diagrams.
First, understand the general rules of automotive circuit diagrams
1 . The wires from the power supply section to the electrical fuses or switches are common to the electrical equipment. It is generally drawn on the upper part of the circuit diagram in the schematic diagram.
2 . The circuit diagram of the standard drawing, the contacts of the switch are at zero or static. That is, the switch is in the off state or the relay coil is in the non-energized state, and the on and off of the device having the switching characteristics such as the transistor and the thyristor are determined depending on the specific conditions.
3 . The characteristics of the car circuit are dual power supply, single wire system, and the electric appliances are connected in parallel with each other, and the relay and the switch are connected in series in the circuit.
4 . Most of the electrical equipment passes through the fuse and is protected by the fuse.
5 . The vehicle circuit is divided into several independent circuit systems according to function and working principle. This can solve the problem that the whole vehicle circuit is large and complicated and difficult to analyze. Now the vehicle circuit is generally drawn according to each circuit system, such as power system, starting system, ignition system, lighting system, signal system, etc. These unit circuits have their own characteristics, grasping the characteristics of the structure of each unit circuit, The principle is thoroughly understood, and it is easy to understand the entire vehicle circuit.
Second, carefully read the circle note carefully read the legend, understand the name of the circuit diagram, technical specifications, clear the meaning of the graphical symbols, establish a one-to-one correspondence between components and graphical symbols, in order to quickly and accurately identify the map.
Third, master the loop In electricity, the loop is a basic, most important, and the simplest concept, any complete circuit is composed of power supply, electrical appliances, switches, wires and so on. For DC circuits, the current always starts from the positive pole of the power supply, and reaches the consumer through wires, fuses, and switches. Then return to the negative pole of the same power supply through the wire (or ground). In this process, as long as there is an error in one link, the circuit will not be correct and effective. For example, starting from the positive pole of the power supply, passing through an electrical appliance (or another electrical appliance), and finally returning to the positive pole of the same power supply, since the potential difference (voltage) of the power supply exists only between the positive and negative poles of the power supply, the power supply The same electrode is equipotential and has no voltage. This "from positive to positive" approach does not produce current.
In the car circuit. Both the generator and the battery are power supplies. When looking for a circuit, you can't confuse it. You can't start from the positive pole of a power supply. After a number of powered devices, return to the negative pole of another power supply, this practice. It does not constitute a true path and does not generate current. So it must be emphasized. The loop is from the positive pole of a power supply, through the electrical appliance, back to the negative pole of the same power supply.
4. Familiar with the switch The switch is the key to the control circuit. The main switch in the circuit often collects many wires, such as the ignition switch and the main switch of the lamp. When reading the picture, pay attention to the five problems related to the switch:
1 . In the many terminals of the switch, pay attention to which is the power supply. Which are the electrical appliances. Whether there are wiring symbols next to the terminal, are these symbols common.
2 . There are several gears in the switch, and which terminals are energized in each gear. Which power is off.
3 . The path through which the battery or generator current reaches the switch, whether it passes through other switches and fuses, whether the switch is manual or electronically controlled.
4 . Each switch controls which appliance is used. What is the function and function of the controlled appliance?
5 . In the controlled appliance. Which appliances are always on and which circuits are briefly connected. Which should be switched on first and which should be switched on later. Which should work alone. Which should work at the same time. Which appliances are allowed to be switched on at the same time.
Fifth, the general method of understanding the map
1 . Look at the whole picture first. Box out the separate system in general. The power and main power switches of the various electrical systems are common. Any system should be a complete circuit and should follow the loop principle.
2 . Analysis of the working process of each system, the relationship between each other Before analyzing an electrical system, it is necessary to understand the functions, functions and technical parameters of the various components included in the electrical system. During the analysis process, special attention should be paid to the working state of the switches and relay contacts. Most electrical systems change the circuit through different working states of switches and relays to achieve different functions.
3, through the analysis of typical circuits, to play the analogy of different types of cars, the circuit schematics, many parts are similar or similar, so through a specific example, give a comparison, compare and contrast. By analogy, you can master some common rules of the car, and then use these commonalities as a guide to understand the circuit principles of other models. You can also find more commonalities and differences between various models.
The versatility and specialized production of automotive electrical appliances make the vehicle circuit form of the same country roughly the same. If you master the characteristics of a certain type of vehicle circuit, you can get an idea of ​​the characteristics of the vehicle circuit of the corresponding model or joint venture.
Therefore, grasp a few typical circuits and master the wiring characteristics and principles of each system. It is good for understanding the circuits of other models.
Introduction and Analysis of Automotive Electrical Circuits With the continuous development and advancement of automotive technology, the application of electrical components in automobiles has become more and more extensive, and as a result, the proportion of maintenance of automotive electrical components has become larger and larger.
Common faults in automotive circuits are: open circuit, short circuit, damage to electrical equipment. In order to diagnose faults quickly and accurately, several common troubleshooting methods are described below.
1) Intuitive Diagnosis When an automobile circuit malfunctions, abnormal phenomena such as smoke, sparks, abnormal noise, burnt odor, and heat may occur. These phenomena can be directly observed, so that the location of the fault can be determined.
2) When the breaking circuit method occurs in the grounding (short circuit) fault of the automobile circuit equipment, it can be judged by the breaking method. After the circuit section suspected of having the ground fault is disconnected, it is observed whether the grounding fault in the electrical equipment still exists, thereby judging the circuit. The location and cause of the grounding.
3) Short-circuit method An open circuit fault occurs in the automotive circuit. It can also be judged by the short-circuit method. That is, the circuit suspected of having an open circuit fault is short-circuited with a screwdriver or a wire, and the change of the pointer of the instrument or the working condition of the electrical equipment is observed, thereby judging the circuit. Is there an open circuit fault?
4) The test light method is to use a car bulb as a test light to check for open circuit faults in the circuit.
5) The instrument method observes the indications of the ammeter, water temperature gauge, fuel gauge, oil pressure gauge, etc. on the dashboard of the car, and judges whether there is any fault in the circuit. For example, if the engine is cold, when the ignition switch is turned on, the water temperature gauge indicates that the full scale position is not moving, indicating that the water temperature sensor is faulty or that the line has ground.
6) The low-voltage grounding test method is to remove a certain wire head of the electric equipment and judge the spark of the metal part of the car (grounding). This method is relatively simple, and is a method frequently used by automobile electricians. The ground test method can be divided into direct grounding and indirect grounding. The so-called direct grounding is a strong spark generated by direct grounding without load. For example, if we want to judge whether the ignition coil to the battery has a fault, please remove the wire connecting the ignition switch on the ignition coil and scratch it on the car body or the frame. If there is a strong spark, the circuit is normal; if not The spark is generated, indicating that the circuit has an open circuit. Indirect grounding is the use of a certain load on a car's electrical appliance to create a weak spark to determine if the line or load is faulty. For example, the traditional ignition system breaker connection line is grounded (the loop passes through the primary winding of the ignition coil). If there is a spark, the line is normal; if there is no spark, the circuit has an open circuit. It is particularly noteworthy that the fire test method cannot be applied to electronic circuit vehicles.
7) High-pressure test method is used to test the high-voltage circuit by ground test, observe the spark condition, and judge the working condition of the ignition system. The specific method is: remove the high-voltage wire of the ignition coil or spark plug, align it with the spark plug or cylinder head, etc., the distance is about 5mm, then turn on the start switch, turn the engine to see the fire. If the spark is strong, it is sky blue, and the slamming sound is louder, it indicates that the ignition system is basically normal; otherwise, the ignition system is not working properly.
The general automotive circuit is a parallel circuit with a single wire system. The positive wires of most circuits (commonly known as the fire wire) are connected to the fuse box, the negative wires (commonly known as the ground wire) are shared, and the important nodes are three, the fuse box, the relay and the combination switch. The criss-crossing car circuits are actually superimposed by various circuits, and each circuit can be separately listed, and the complexity is simple. The vehicle circuit can be divided into lights, signals, meters, start, ignition, charging and other circuits according to the purpose. Each circuit has its own wire connected to a control switch or fuse box.
Most of the wires are connected to fuses or switches at one end and relays or powered devices at the other end. For example, the headlight circuit is divided into two chromes, one is the power branch, that is, the fuse box (positive line) -> headlight relay -> headlight -> negative line, the other is the control branch, that is, the fuse box -> combination switch -> Headlight relay -> negative line. Other circuits such as small lamps, brake lights, turn signals, compartment lights, wipers and the like are basically similar.
The fuse box on the general car is placed in the same place as the relay for easy inspection. Also understand the function of the combination switch, especially the function of the wires on the combination switch connector. If you know the role and position of three important nodes, such as fuse box, relay and combination switch, it is easier to get started by comparing the relevant electrician books.
First, the composition of the vehicle circuit The vehicle complete circuit usually has a power circuit, starting circuit, ignition circuit, lighting and lighting signal device circuit, instrument information system circuit, auxiliary device circuit and electronic control system circuit.
1. The power circuit is also called the charging circuit. It is a circuit composed of a battery, a generator, a regulator and a charging indicating device. The power distribution (distribution) and circuit protection devices can also be classified into this circuit.
2. The starting circuit is a circuit consisting of a starter, a starter relay, a starter switch and a start-up protection circuit. It is also possible to include a device for starting preheating under low temperature conditions and its control circuit in this circuit.
3. The ignition circuit is a circuit unique to gasoline engine vehicles. It consists of an ignition coil, a distributor, an electronic ignition controller, a spark plug and an ignition switch. Microcomputer controlled electronic ignition control systems are generally included in the engine electronic control system.
4, lighting and lighting signal device circuit is composed of headlights, fog lights, position lights, turn signals, brake lights, backup lights, interior lights and related control relays and switches.
5. The instrument information system circuit is a circuit consisting of a meter and its sensors, various alarm indicators and controllers.
6. The auxiliary device circuit is a circuit composed of various electrical devices provided for improving safety, comfort, and the like of the vehicle. The types of auxiliary electrical devices vary from model to vehicle. The higher the car grade, the better the auxiliary electrical device. Generally, it includes a windshield wiper and cleaning device, a windshield defrosting (anti-fog) device, an air conditioner, and an audio device. The higher-grade models are also equipped with window electric lifts, electronically controlled door locks, power seat adjustments and electric remote control rearview mirrors. Electronically controlled airbags fall under the electronic control system.
7. The electronic control system circuit mainly consists of the engine control system (including fuel injection, ignition, emission and other control), automatic transmission and constant speed driving control system, brake anti-lock braking system, airbag control system and other circuits.
Second, three kinds of circuit diagram 1, wiring diagram wiring diagram according to the general position of the car electrical equipment on the body to carry out wiring.
Its characteristics are: the number of electrical appliances (ie electrical equipment) of the whole vehicle is obvious and accurate, the direction of the electric wires is clear, and there is a beginning and a end, which is convenient for tracking and tracking, and it is convenient to find. It distributes the wires to each harness in a harness configuration to strictly match the position of each plug-in. The relationship between the wiring and the gear control of the switch is shown in the form of a table near each switch, indicating the connection relationship between the fuse and the wire, indicating the color and cross-sectional area of ​​the wire.
Disadvantages of the wiring diagram: the wires on the drawing are criss-crossed, the printed layout is small, it is difficult to distinguish, and the layout is too large. The reading and drawing are time-consuming and laborious, and it is difficult to grasp the key points and difficulties of the circuit; it is difficult to express the internal structure and working principle of the circuit. .
2. Schematic diagram â—‡ The schematic diagram of the whole vehicle circuit:
For production and teaching needs, it is often necessary to find the beginning and end of a circuit as soon as possible in order to determine the route of failure analysis. When analyzing the cause of the fault, it cannot be limited to a certain part in isolation, but the position of this part of the circuit in the whole vehicle circuit and the connection with the relevant circuit are expressed. The advantages of the vehicle circuit diagram are:
(1) There is a complete concept for the whole vehicle circuit. It is both a complete vehicle circuit diagram and a cross-connected partial circuit diagram. The key points are difficult, complicated and appropriate.
(2) The concept of high potential and low potential is established on this graph: its negative "-" grounding (commonly known as grounding), the lowest potential, can be represented by the lowermost line in the figure; the positive "+" potential is the highest, the most The line above shows. The direction of the current is basically from top to bottom, the path is: the positive pole of the power supply "+" → switch → electrical appliance → grounding → the negative pole of the power supply “-â€.
(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 shape and internal structure of the components, which is convenient for readers to associate, analyze, easy to read and easy to draw.
(4) The local circuits (or subsystems) are connected in parallel and have a clear relationship. The connection point between the generator and the battery and between the subsystems is kept as close as possible. The connection of the fuses, switches and meters is basically the same. The original picture is consistent.
局部 Partial circuit schematic:
In order to clarify the internal structure of the automotive electrical equipment, the relationship between the various components, to understand the working principle of a certain local circuit, often extract a certain local circuit from the vehicle circuit diagram, refer to other informative materials, necessary At the time, according to the field mapping, inspection and test records, the key parts are enlarged, drawn and explained. This kind of circuit diagram has less electric appliances and smaller format, which is simple and clear, easy to read and easy to draw; its shortcoming is that it can only understand the part of the circuit. Figure 8-7 shows the circuit schematic of the Poussin engine section.
3, wire harness diagram The whole vehicle circuit harness diagram is often used for connection, overhaul and wiring of the assembly line and repair shop of the automobile factory. The wire harness diagram mainly indicates the connection position of each electric harness of the electric wire bundle, the mark of the terminal post, the wire end, the shape and position of the connector (connector), etc., which is a circuit diagram of a car that can be physically contacted by a vehicle. Such a figure generally does not describe in detail the direction of the wire inside the wire harness, and only the wire ends and the connector outside the wire bundle are numbered or marked with letters. It is a circuit representation that highlights the assembly marks and is very easy to install, wire, test and repair. If you use the serial number and color of the figure to mark it correctly and use it in combination with the circuit schematic and wiring diagram, it will play a greater role and receive better results.
Third, the general automotive circuit wiring rules Automotive lines are generally used in a single-wire system, electrical equipment in parallel, negative grounding, line color and number to distinguish, and the ignition circuit as the center of the whole car circuit into several main lines, namely: Battery fire wire (line 30), accessory fire wire (Acc wire), key switch fire wire (line 15).
(1) Battery FireWire (B or 30)
The straight-through fuse box is taken out from the positive electrode of the battery, and the battery fire wire of the automobile is also connected to the fire line terminal of the starter, and a fine fire line is taken out from there.
(2) Ignition instrument indicator line (IG line or line 15)
The ignition switch has electric wires in the ON (operating) and ST (starting) gears. The car key must be used to connect the ignition system, pre-magnetization, instrument system, indicator light, signal system, and electronic control system.
(3) Dedicated line (Acc line or 15A line)
It is used for electrical appliances that need to be connected when the engine is not working, such as a radio, a cigarette lighter, etc. The ignition switch is separately set to provide power for the first gear, but the radio and the like need to be connected to the ignition indicator light at the same time when the engine is running, so the contact structure of the ignition switch and the contact should be specially designed.
(4) Start control line (ST line or line 50)
The control switch (touch pad) of the main circuit of the starter is commonly used to open and close. The attracting coil and the holding coil of the magnetic switch can be controlled by the starting gear of the ignition switch. The attraction 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. The starter relay must be set up separately (such as Dongfeng, Liberation and Mitsubishi Heavy Industries). car). In the car equipped with an automatic transmission, in order to ensure the start of the neutral gear, there is often a neutral switch on the 50th line.
(5) Ground wire (grounding wire or line 31)
In the automotive circuit, the wiring method of the component and the metal part of the body (frame) as a common wire is called a single wire system, and the part where the body and the electrical device are connected is called grounding or grounding. The grounding points are distributed throughout the car. Due to the contact of different metals (such as iron, copper and aluminum, lead and iron), the electrode potential difference is formed. Some ground parts are easily contaminated with muddy water, oil or rust, and some ground parts are very Thin sheet metal parts may cause poor grounding, such as the light is not bright, the meter does not work, and the speaker does not ring. It is necessary to attach the same importance to the grounding joints and the firewire joints. Therefore, the modern automobile adopts a two-wire system, and has a special public grounding joint. The special grounding diagram of the iron and steel is drawn, which is juxtaposed with the outline of the fuse circuit. In order to reduce the line contact pressure drop during starting, the battery pole clamp, the frame and the engine body are connected with a large cross-sectional area, and the contact parts are completely derusted, lacquered and tightened.
Fourth, the general points of reading the circuit diagram (1) Throughout the "full car", eye-catching "local" - from "concentration" to "distribution."
The whole vehicle circuit is generally composed of various partial circuits, which express the connection and control relationship between the respective partial circuits. To separate the partial circuit from the overall vehicle map, it is necessary to grasp the basic conditions and wiring rules of each unit circuit.
The basic characteristics of the automotive circuit are: single-wire system, negative grounding, and electric appliances connected in parallel. Each unit (partial) circuit, such as power system, starting system, ignition system, lighting system, signal system, instrument system, etc., has its own characteristics. Seeing the circuit should be guided by its own characteristics, to decompose and study all The car circuit, this will be less blind, and can read the car circuit diagram more quickly and accurately. At the beginning, you must carefully read the legends several times. Check the approximate location and quantity of the electrical appliances on the vehicle according to the circuit diagram. The use of electrical appliances, whether there are novel and unique electrical appliances, if any, should pay more attention.
(2) Grab the role of the "switch" - the "object" controlled. The switch is the key to control circuit switching. Pay special attention to the relay, not only the control switch but also the controlled object.
(3) Find the "loop" of the current - the "pathway" of the control object.
The loop is the simplest electrical concept. Regardless of the electrical appliance, in order to work properly (convert electrical energy to other forms of energy), it must form a path with the positive and negative poles of the power source (generator or battery). That is: starting from the positive pole of the power supply → through the electrical appliance → return to the negative pole of the same power supply. This simple and important principle must be used whenever you read a circuit diagram. When reading a car circuit, it is often overlooked.
Wiring rules of automobile circuits The characteristics and general rules of automobile wiring are: generally adopting single-wire system, paralleling of electric equipment, negative grounding, and different lines and numbers of lines, and dividing into several mains with ignition switch as the center. Trunk line.
1. Battery positive line: The straight-through fuse box is taken out from the battery, and some are directly led from the positive battery line to the positive terminal of the starter, and then the thin positive line is taken to other circuits.
2, ignition, instrument, indicator light: must pass the car key to connect the circuit.
3, dedicated line: no matter the engine work needs to access the electrical appliances, such as the lighter cigarette lighter, etc., the ignition switch is set to a separate gear to supply power.
4, start the control line: start the main circuit of the control switch (touch pad) commonly used magnetic switch to open and close. There are three forms of wiring: the suction coil of the magnetic switch of the small power starter keeps the coil controlled by the starting gear of the ignition switch; the suction and holding coil of the high-power starter is controlled by the starter relay (such as Dongfeng Jiefang and Mitsubishi heavy-duty truck); - For cars with automatic transmission, in order to ensure neutral start, the start control line is often connected in series to the neutral switch.
5, the ground wire: the ground point is distributed in the body of the car, and the connection of different metals (such as iron, copper and aluminum, aluminum and iron) to form electrode potential difference, some ground parts are prone to muddy oil or rust, some The iron part is a very thin sheet metal sheet, which may cause bad grounding. If the lamp is not bright, the meter does not work, and the speaker does not ring. Therefore, some cars use double-wire.
Second, the power system wiring rules 1, the generator and the battery in parallel, the battery negative must be grounded. The positive pole of the battery is connected to the positive pole of the motor through the ammeter (or directly). The static electromotive force of the battery is often between 11.5V and 13.5V, and the output voltage of the generator is often limited to between 13.8V and 15V (24V to 28V for 24V). When the generator is working, the normal voltage is 0.3~3.5V higher than the battery voltage. This is mainly to overcome the line voltage drop, so that the battery can be fully charged when it is charged, and it will not be overcharged. 2. There is a mark or name next to the terminal of the domestic silicon rectifier generator. “Ten†or “B ten†is the “armature†terminal. This terminal should be connected with the “10†pole of the ammeter or battery; “F†It is a "magnetic field" terminal that is connected to the "magnetic field" terminal of the regulator; "E" is a "grounding" terminal that should be connected to the "grounding" terminal of the regulator.
3. The magnetic field coil of the alternator with external regulator is grounded by two types: one is that the magnetic field coil is directly grounded inside the generator, such as the generator of the domestic Dongfeng EQ1092 BJ2020 automobile; the other is that the magnetic field coil is not The generator is grounded inside, but it is grounded by a regulator, such as an AC generator that liberates the CA1092.
Third, start the system wiring rules 1, the ignition switch directly controls the starter's circuit: the ignition switch directly controls the starter suction and hold coil in the start gear, mostly used for the car circuit of the starter below 1.2KW; the starter of the 1.5KW or more The current of the magnetic switch coil is above 40A, and the start relay contact is used as the switch.
2. Starter control circuit with start-up protection: When the ignition switch is turned on at 0, the circuit is disconnected. The power supply line of the ignition switch in the first gear (not started) is: the generator excitation ignition coil meter lights up. When the ignition switch is in 2nd gear, in addition to turning on the above circuit, the starter relay circuit must be turned on: battery positive - current meter - ignition switch - starter relay coil - relay normally closed contact - grounding - Battery negative - starter drive host. At the same time, the contact bridge turns the ignition coil bypass contact on, the current passes through the ignition coil primary, and the additional resistor is isolated. After the engine is ignited, the ground voltage of the generator neutral point N (about 0.5 of the generator regulation voltage) causes the normally closed contact of the start protection relay in the start relay to be disconnected, and the charging indicator is turned off, and the charging indication is turned off. The light goes out, indicating that the generator is working properly. At the same time, the grounding circuit of the starting relay coil is also cut off. When the generator is working normally, even if the ignition switch is mistakenly moved to the second gear, the starting machine will not mesh with the flywheel, avoiding breaking the flywheel ring gear and the starting machine, Protect the role of the starter.
Fourth, the ignition system wiring rules Car ignition system can be divided into ordinary (with contact) ignition system, non-contact ignition system, microcomputer control ignition system, etc., the working process is basically in the following sequence: primary current ——Primary current cut-off (this is just a certain angle before the piston is at the top dead center of compression) – the primary coil produces self-induced electromotive force (about 300V) – the secondary coil mutual inductance produces pulse high voltage (about 6000~30000V) - The spark plug has an electric spark.
The ignition module of the non-contact ignition system must have the lead wire: 2 power input lines controlled by the ignition switch (4, 5 feet), and the signal input line from the signal generator (the signal generator and the distributor shaft are integrated) 3 (5, 5, 3 feet, 5 of which are for the signal generator's power line), and the primary current input and output lines 2 (1, 2 feet).
Fifth, the wiring system of the lighting system The car lighting system is generally composed of headlights, width lights (position lights), tail lights (post-width lights), license plate lights, instrument lights, indoor lights, etc., of which the headlights are divided into High beam and low beam, controlled by dimmer switch. The light is controlled by the light switch: the light switch is turned off in the 0th gear, the 1st gear is not lighted (including the light, the tail light, the instrument light, the license plate light), the second gear is the headlight, and the small light is on at the same time. The current of the lighting system generally comes from the positive pole of the battery and is not controlled by the ignition switch (due to the high power of the headlights, the light relay is commonly used to control the on/off, and the second gear of the switch is used to control the relay coil). The overtaking light signal is usually indicated by the high beam off, and the signal is not passed when the signal is sent. Modern car lighting systems are commonly used in combination control. The combination switch is mounted on the steering column and is located on the underside of the steering wheel. The driver's receiver can ignore the steering wheel during operation.
Sixth, the instrument alarm system wiring rules 1, all electrical instruments are controlled by the ignition switch.
2. The meter head of each meter is connected in series with its sensor. The fuel gauge and water temperature gauge are generally connected with an instrument regulator.
3. The ammeter is connected in series between the positive pole of the generator and the positive pole of the battery. The generator charging current enters from the positive pole of the ammeter, and the pointer is biased toward the positive end. When the battery is discharged outward, the pointer is biased toward the negative end. The two currents do not pass through the ammeter: the load current exceeding the current meter range, such as the starter, glow plug, and horn lamp current: the current supplied to other loads during normal operation of the generator. Note: When the generator is not working, the current supplied by the battery to other loads must pass through the ammeter. Modern car multi-purpose charging is just a replacement for the ammeter. The disadvantage is that the charge and discharge current is not known, and overcharging is not easy to find.
4. The voltmeter is connected in parallel after the ignition switch, and the system voltage is displayed only when the ignition switch is turned on. 12V system often uses 10V~18V, 24V electric system often uses 20~36V voltmeter.
5. The indicator light and the warning light are often arranged in the assembly or in the vicinity of the instrument. They are controlled by the working (ON) and starting (ST) of the ignition switch together with the instrument. In the ON file, it should be able to check whether most of the meters, indicators, and warning lights are good. The indicator light and the warning light can be divided into two types according to the circuit connection method: one is that the light bulb is connected to the ignition switch fire line, and the external sensing switch: when the switch is turned on, the ground is formed with the grounding, and the light is bright. Such as: charging indicator light, hand brake indicator light, brake liquid level warning light, door not closed alarm light, oil pressure warning light, water level low alarm light, etc. Another connection is to indicate that the bulb is grounded and the control signal is from the live end of the other switch. Such as: high beam indicator, turn indicator light, seat belt without indicator light anti-lock brake indicator (ABS), cruise control indicator.
6, the automobile instrument commonly used bimetal electric heating wire structure, the head of the meter usually only has 2 lines. For example, the two terminals of the fuel indicator are arranged up and down. In general, the upper terminal should be connected to the power line, and the lower terminal should be connected to the sensor, otherwise it will not work normally. In addition, there is a double coil cross. *, the instrument with a magnetic pointer in the middle oil is taken as the 3-wire lead, one of which is connected to the ignition switch, the other is grounded, and there is a line-connected sensor. Mechanical instruments are not connected to the circuit, such as the speed odometer of the flexible shaft transmission, the direct-acting curved spring type brake pressure gauge, the oil pressure gauge, the ether expansion water temperature gauge, the oil temperature gauge, etc. High, but the introduction of many pipelines, flexible shafts into the instrument panel, disassembly and assembly, and even easy to leak, is gradually being replaced by electronic control instruments.
7. Signal system wiring rules Signal system main oil turn signal, hazard warning signal, brake signal, reversing signal, horn, etc. These signals are sent by the driver to other vehicles and pedestrians according to road traffic conditions. Strong randomness, generally * self-switch control such as brake signal is controlled by the brake pedal linkage: the reverse light is controlled by the shift lever reverse shaft linkage, and can be turned on without the driver's intentional operation. On the plate, the driver can signal without leaving the steering wheel.
1. The turn signal light has a certain flash frequency. The national standard specifies 60-120 magnetic/min. The Japanese regulations are (85+10) times/min. The turn signal power is usually 21~25W. Both front and rear are set. Large vehicles and cars often There is also a turn signal on the side. The circuit is generally connected: the turn signal and the turn signal switch and the flashing relay are connected in series with the normally closed contact of the hazard warning light switch and the ignition switch, that is, the turn signal light is used when the ignition switch is in the working position (ON).
2, the use of hazard warning lights are mainly: the car is faulty or dangerous can not drive: the car has the task of pulling the car, need his car to pay attention: the car needs priority to pass, need his car to avoid. Therefore, the hazard warning light can be used when the engine is not working. At this time, it is not necessary to turn on the ignition system and the instrument warning light. For this purpose, there is a hazard warning switch, which is a multi-knife linkage switch, while disconnecting the ignition switch wiring, Connect the battery wiring, the flasher and the lamp power supply directly from the battery, and connect the output of the flash relay to the left and right turn signals. That is, when the flash relay is activated, the left and right turn signals and the indicator lights simultaneously emit a danger signal.
Eight, electronic control system wiring rules 1, understand the function of the electronic control system, which components are controlled, which physical quantities are controlled. For example, some control ignition, some control fuel injection, and some control automatic transmission.
2. Master the name, installation location, function, structural principle and main technical parameters of each sensor. For example, the resistance value in the power-off state, the potential and the current in the power-on state, and whether the signal voltage of each sensor is an analog quantity, a pulse quantity, or a switching quantity.
3. Master the names, installation locations, functions, structural principles and main parameters of various actuators.
4. Understand the functions of the main functional blocks inside the computer, master the serial number of the terminals between the sensors and actuators, the letter code, and the normal voltage or resistance between the terminals.
5. Understand the installation position of the computer, each sensor and each actuator in the vehicle, distinguish the serial number and code of each connector and its terminals, and distinguish the shape characteristics of each component.
6. Understand the fault diagnosis socket or detector communication interface, find the fault code table of each vehicle according to country, manufacturer and vehicle dispatch, read the fault code with the flash condition of the instrument or fault check light, determine the fault location, and eliminate the fault.
The wiring rules of the electronic control system circuit can be summarized as follows: the computer control circuit must accept the ignition switch control, and various sensors must input the working condition signal at any time. For example, the magnetic pulse type or Hall type sensor can generate the pulse voltage signal: some sensors are Made of thermistor, the resistance value changes, and the output voltage also changes. It belongs to the analog voltage signal, such as water temperature, intake air temperature sensor, etc.: The electronic control system actuator is controlled by computer and has self-diagnosis function. Computer work generally consists of two modes - open loop and closed loop control. For example, the open-loop control of fuel injection: after the engine computer receives the input signal, it only responds according to the preset procedure, and the signal of the oxygen sensor is not monitored. The open-loop working conditions include warm-up working conditions, deceleration conditions, and full throttle operating conditions. Closed-loop control: The engine computer detects the oxygen sensor signal, so that the computer-controlled injection pulse width is ideally air-fueled to achieve the best fuel economy and low emissions. The closed-loop working conditions include idle working conditions and cruise working conditions.
9. Wiring precautions 1. Prepare the circuit schematic diagram of the vehicle to be connected. If there is no circuit diagram, it is best to draw a wiring sketch with the actual object, which will bring great convenience to the wiring maintenance work.
2, due to temporary external wiring for maintenance, you must pay attention to insulation to prevent short circuit.
3. Do not use live wiring. When the wire is damaged, replace the wire of the original standard model. The connection should be *, and the contact resistance at the connection should be minimized.
4. After the wiring is completed, it should be tied and handled according to the original wiring requirements.
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