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Basic knowledge of automotive wiring harness

Automotive wiring harness

Automobile wiring harness (automobile wiring harness) realizes the physical connection of the power supply and various electrical parts on the automobile. The wiring harness is distributed all over the vehicle. If the engine is compared to the heart of a car, then the wiring harness is the neural network system of the car, which is responsible for the information transmission between various electrical parts of the vehicle.

There are two types of systems for manufacturing automotive wiring harness

(1) Divided by European and American countries, including China, TS16949 system is used to control the manufacturing process.

(2) Mainly in Japan: Toyota, Honda, they have their own system to control the manufacturing process.

Automobile wiring harness manufacturers have their own particularity and attach importance to cable production experience and cable cost control. The world's large wire harness plants are mostly based on wires and cables, such as Yazaki, Sumitomo, Leni, Guhe, Fujikura, kelop, Jingxin, etc

Brief introduction of common materials for automotive wiring harness

1. Wire (low voltage wire, 60-600v)

Types of wires:

National standard line: QVR, QFR, QVVR, qbv, qbv, etc

Daily marking: AV, AVS, AVSS, AEX, AVX, cavus, EB, TW, she-g, etc

German marking: flry-a, flry-b, etc

American line: Sxl, etc

The common specifications are wires with nominal sectional area of 0.5, 0.75, 1.0, 1.5, 2.0, 2.5, 4.0, 6.0 square mm

2. Sheath

The sheath (rubber shell) is usually made of plastic. The conductor of the pressed terminal is inserted into it to ensure the reliability of connection. The material mainly includes PA6, PA66, ABS, PBT, PP, etc

3. Terminal

A shaped hardware component, which is crimped on the wire to connect different wires to transmit signals, including male terminal, female terminal, ring terminal and circular terminal, etc.

The main materials are brass and bronze (the hardness of brass is slightly lower than that of bronze), and brass accounts for a large proportion.

2. Sheath accessories: Waterproof bolt, blind plug, sealing ring, locking plate, clasp, etc

It is generally used to form connector with sheath terminal

3. Through hole rubber parts of wire harness

It has the functions of wear resistance, waterproof and sealing. It is mainly distributed at the interface between the engine and the cab, the interface between the front cabin and the cab (left and right in total), the interface between the four doors (or back door) and the car, and the fuel tank inlet.

4. Tie (clip)

An original, usually made of plastic, is used to hold the wiring harness in the car. There are ties, bellows lock ties.

5. Pipe material

Divided into corrugated pipe, PVC heat shrinkable pipe, fiberglass pipe. Braided pipe, winding pipe, etc. To protect the wiring harness.

① Bellows

Generally, about 60% or even more bellows are used in bundle binding. The main feature is good wear resistance, high temperature resistance, flame retardant and heat resistance are very good in high temperature area. The temperature resistance of bellows is - 40-150 ℃. Its material is generally divided into PP and pa2. PA is better than PP in flame retardancy and wear resistance, but PP is better than PA in bending fatigue.

② The function of PVC heat shrinkable pipe is similar to that of corrugated pipe. PVC pipe flexibility and bending deformation resistance is good, and PVC pipe is generally closed, so PVC pipe is mainly used at the branch of the harness bend, so as to make the wire smooth transition. The heat resistance temperature of PVC pipe is not high, generally below 80 ℃.

6. Tape

Production tape: wound on the surface of wire harness. (divided into PVC, sponge tape, cloth tape, paper tape, etc.). Quality identification tape: used to identify the defects of the production products.

The tape plays the role of binding, wear resistance, insulation, flame retardant, noise reduction, marking and other functions in the wire bundle, which generally accounts for about 30% of the binding materials. There are three kinds of tape for wire harness: PVC tape, air flannel tape and cloth base tape. PVC tape has good wear resistance and flame retardancy, and its temperature resistance is about 80 ℃, so its noise reduction performance is not good and its price is relatively low. The material of flannel tape and cloth base tape is pet. The flannel tape has the best binding and noise reduction performance, and the temperature resistance is about 105 ℃; the cloth tape has the best wear resistance, and the maximum temperature resistance is about 150 ℃. The common disadvantages of flannel tape and cloth base tape are poor flame retardancy and high price.

Knowledge of automobile wiring harness

Automobile wiring harness

Automobile wiring harness is the main body of automobile circuit network. Without wiring harness, there will be no automobile circuit. At present, whether it is a luxury car or an economy car, the wiring harness is basically the same, which is composed of wires, connectors and wrapping tape.

Automobile wire is also called low-voltage wire, which is different from ordinary household wire. Ordinary household wire is copper single core wire, with a certain hardness. The car wires are copper multi core flexible wires, some of which are as thin as hair. Several or even dozens of soft copper wires are wrapped in plastic insulated pipes (PVC), which are soft and not easy to break.


The common specifications of wires in automotive wiring harness include wires with nominal cross-sectional area of 0.5, 0.75, 1.0, 1.5, 2.0, 2.5, 4.0, 6.0, etc. each of them has allowable load current value, which is used for wires of different power consumption equipment. Take vehicle harness as an example, 0.5 specification line is applicable to instrument lamp, indicator lamp, door lamp, ceiling lamp, etc.; 0.75 specification line is suitable for license plate lamp, front and rear small lamps, brake lamp, etc.; 1.0 specification line is suitable for turn signal lamp, fog lamp, etc.; 1.5 specification line is suitable for headlamp, horn, etc.; main power line such as generator armature wire, grounding wire, etc. requires 2.5-4mm2 wire. This only refers to the general car, the key depends on the maximum current value of the load. For example, the ground wire of the battery and the positive power line are used separately for the automobile wires. Their wire diameters are relatively large, at least more than ten square millimeters. These "Big Mac" wires will not be incorporated into the main harness.

Before arranging the wiring harness, the wiring harness diagram should be drawn in advance, which is different from the circuit schematic diagram. Circuit schematic diagram is an image that describes the relationship between various electrical parts. It does not reflect how electrical components are connected with each other, and is not affected by the size and shape of each electrical component and the distance between them. The wiring harness diagram must take into account the size and shape of each electrical component and the distance between them, and also reflect how the electrical components are connected with each other.


After the technician of the wiring harness factory makes the wiring harness wiring board according to the wiring harness drawing, the worker will cut the wire and wire according to the regulations of the wiring board. The main harness of the whole vehicle is generally divided into engine (ignition, EFI, power generation, starting), instrument, lighting, air conditioning, auxiliary electrical appliances and other parts, including main harness and branch harness. A vehicle main harness has multiple branch wiring harness, just like tree pole and branch. The instrument panel is the core part of the main harness of the whole vehicle, which extends back and forth. Due to the length relationship or convenient assembly and other reasons, the wiring harness of some vehicles is divided into head harness (including instrument, engine, front light assembly, air conditioner, battery), rear harness (tail lamp assembly, license plate lamp, trunk lamp), roof harness (door, ceiling lamp, sound horn), etc. Each end of the harness will be marked with numbers and letters to indicate the connection object of the wire. The operator can see that the sign can be correctly connected to the corresponding wires and electrical devices, which is particularly useful when repairing or replacing the harness. At the same time, the color of wire is divided into single color line and double color line. The purpose of color is also specified, which is generally the standard set by the vehicle manufacturer. China's industry standards only stipulate the main color, for example, single black is used for grounding wire, red monochrome is used for power line, which can not be confused.

Wire harness is wrapped with woven wire or plastic tape. For safety, processing and maintenance convenience, woven wire wrapping has been eliminated. Now it is wrapped with adhesive plastic tape. Connector or lug is used for connection between harness and harness and between harness and electrical parts. The connector is made of plastic and has plug and socket. The wiring harness is connected with wire harness by connector, and the connection between harness and electrical parts is connected by connector or lug.

With the increase of automobile function and the widespread application of electronic control technology, more and more electrical components, more and more wires, and the wire harness will become thicker and heavier. Therefore, the advanced automobile has introduced the CAN bus configuration, uses the multiplex transmission system. Compared with the traditional wiring harness, the number of wires and connectors is greatly reduced, which makes the wiring easier.