What is a car circuit diagram?

Circuit symbols and meanings of Volkswagen.

General component letter code meaning

In the circuit diagram of Volkswagen, the electrical components are the main part of the circuit diagram, and the electrical components are represented by block diagrams, supplemented by corresponding codes. Usually, components are marked with letters or a combination of letters and numbers, and each component has a code name, such as A for battery, B for starter and C for alternator. Knowing the meaning of these letters is of great help to the reading and maintenance of circuits. The following table lists the meanings of the letter codes of common parts of Volkswagen.

Wiring code description

In the circuit diagram of Volkswagen, the connection points of circuit elements are marked with connection codes. No matter where these codes appear in the circuit, the same codes represent the same contacts. As shown below, there are two connection codes on the starter B, namely, the contacts of 30 and 50, and there are also two contacts of 30 and 50 on the ignition switch D. The codes of these two components are connected between 30 and 30, and the No.30 line represents a constant power supply, which is directly connected to the positive electrode of the battery and is not controlled by the ignition switch. Codes 50 and 50 are also concatenated. The line 50 is controlled by the ignition switch. Only when the ignition switch is in the start position, the line 50 is energized and supplied to the load circuit.

Description of common wiring codes of Volkswagen circuits is shown in the following table.

Fuses and relays

In Volkswagen cars, fuses and relays mostly use central distribution boxes, such as Jetta, Passat and Santana cars. The picture below shows the central distribution box of Jetta, which contains almost all the fuses. The central distribution box is installed on the upper part of the brake pedal. The fuse of the whole vehicle is different due to different vehicle configurations, and the fuse capacity is distinguished by different colors. The fuse of the whole vehicle is rarely set near the battery. Almost all relays are concentrated in the central distribution box, and the whole vehicle has 6 ~ 12 or 24 relays. Almost all the main wiring harnesses are plugged in from the back of the central distribution box and then lead to various electrical appliances, so the wiring harness of the whole vehicle is also concentrated near the dashboard of the cab.

At present, most of the new Volkswagen models use the vehicle power control unit J5 19 as the central distribution box. It has the functions of power terminal control, lighting control, wiper control, turn signal control, windshield heating, personalized setting and so on.

In the new model, the fuse box is also self-contained and not mixed with relays. Some fuse boxes are installed under the left dashboard and some are installed under the right dashboard, as shown in the following figure. Usually, manufacturers will give the locations and names of various types of fuses and relays in the maintenance manual for readers' reference.

Wire description

Volkswagen's circuit diagram shows two kinds of circuit connections, internal connection and external connection, as shown in the following figure.

The internal connections are drawn with thin lines. This part of the connection exists, but the line does not exist. Marking the circuit is only to illustrate this connection and make the circuit diagram easier to understand.

External wiring is drawn with thick solid lines on the drawings, and each line is marked with the color and cross-sectional area of the conductor. The colors of circuit wires are indicated by letters. When the conductor is bicolor, the letters * * * of the two colors should be marked together, with the front as the main color and the back as the auxiliary color, such as sw/ge, li/ws, etc. The cross-sectional area of the wire is marked with a number above the color of the wire.

Characteristics of Volkswagen Circuit Diagram

1. The circuit diagram of the whole vehicle consists of three parts.

Volkswagen's circuit diagram is divided into three parts, as shown in the figure below. The first part is the central distribution box circuit, indicating the position and capacity of fuse, the position number and terminal number of relay, etc. The second part is the electrical components and circuits in the car; The bottom horizontal line is the ground wire, marked with the circuit number and the location of the grounding point. In the third part, the label of the grounding wire is artificially compiled and does not exist in the physical object. The purpose of this is to point out where the other end of the loop connection line is on a page and find the conductor conveniently.

2. The problem of horizontal connection is solved by using polyline coding method.

The circuit diagram adopts the broken line coding method to solve the problem of line crossing. For some equipment with complex circuits (such as headlights), it involves ignition switch, light switch, dimmer switch and other power distribution equipment, and these three switches are not on the same vertical line. If you use the traditional drawing method, you need to draw some horizontal lines to connect them, so there will be more horizontal lines on the picture, which will increase the difficulty of reading the picture. Therefore, the general circuit diagram of this circuit diagram adopts the broken line coding method. As shown in the above figure, the upper part of the starter circuit wire is at the position of circuit number "13" and the lower part is at the position of circuit number "18". The processing method in the figure is to draw a small box at the end of the upper half circuit with the internal standard "18", indicating that the lower half circuit should be in the position of the number "18". There is also a small box at the beginning of the lower part of the circuit, with the internal standard "13", indicating that the upper part of the circuit should be found at the position of the number "13". Through the above four numbers, the upper and lower circuits are organically linked together, thus solving the problem of line crossing.

3. The circuits are vertically distributed.

The main line is drawn by vertical lines, and there is no wire crossing on the drawing. The central junction box only adopts horizontal line drawing method, and there are many horizontal lines. In addition to 15, 30, 3 1 50 and x, there are some temporarily numbered lines, such as a, b, c, d, e, g, h, m.

4. Marking method of grounding wire

On the ground wire, circled numbers (or letters and numbers) are usually used to indicate different grounding points in the circuit. As long as the numbers (or letters and numbers) in the circle are the same, it means that they belong to the same grounding point. Through these circled numbers, the position of the grounding point in the car body can be found in the description of the circuit diagram, as shown in the following figure.

5. It also shows the line structure and indicates the line direction.

The whole electrical system of the car is controlled by the central distribution box (also called fuse-relay socket board), and most relays and fuses are installed in front of the central distribution box. Connectors and sockets are installed on the back of the central distribution box. The J 18-X contact unloading relay in the above figure is marked with 13/30, 14/85, 12/87 and 1 1/86 in the circuit and schematic diagram respectively. Among them, molecular numbers 13, 14, 12, 1 1 refer to the jack position of the X-contact unloading relay on the central distribution box (figure A below), and denominator numbers 30, 85, 87 and 86 refer to the four pins on the relay.

▲ Figure A Relay Location Map

▲ Figure b X Contact Unloading Relay Pin

The numbers on the denominator have the following meanings:

85: Used for grounding, i.e. grounding wire or negative battery grounding wire.

8: Used to connect the power cord controlled by the ignition switch, that is, the conditional power cord (such as 15 line or X-ray).

30: Used to connect the positive electrode of the battery, and there is always electricity or constant electricity.

87: Power cord controlled by relay contacts. When the conditional power supply is energized, wires 85 and 86 are turned on, and the relay coil generates magnetism, which attracts the contact between wires 30 and 87 to close, so that the electrical appliance is energized.

Reading examples

The following are examples of new sagitar batteries, starters, alternators, and on-board power grid control unit circuits (below).

As can be seen from the circuit diagram, the positive electrode "+"of the battery has two connection modes, one is connected to the terminal of the starter 30; The other is connected to the bolt on the electrical cabinet.

The 30th end of the starter is connected to the positive power supply end of the battery; Terminal 50 is a start-up control terminal, which is connected to the wire with code 46 in the box.

The "B+" terminal of the alternator is a voltage output terminal, which is connected to the fuse SA 1 of 200A. The "L" terminal is the control terminal of the charging indicator lamp, which is connected to the T52c/32 terminal of the power grid control unit after passing through the plug connector T4t/2 and the connection (6 1) in the vehicle interior space harness. The "DFM" terminal is the output terminal of the alternator feedback signal, and is connected with the conductor code 68 in the box through the connector T4t/ 1.

The main relay J27 1 is installed on the electric cabinet on the left side of the engine compartment together with the fuse holder SB, and the 86 pins of the main relay are power terminals; Pin 85 is the control terminal, which passes through terminal 62 of the electric control box and is connected to the conductor with code 66 in the box. It is actually controlled by the engine control unit. When the corresponding terminal of the engine control unit outputs a low voltage signal, the main relay coil is energized, the main contact of J27 1 is turned on, and the 87th line and the 30th line of the main relay are turned on, and the battery voltage is supplied to the relevant electrical equipment respectively. Source: automobile maintenance technology and knowledge