Automobile manufacturing method and inspection harness replacement

1. Function of automotive wiring harness

In order to make the car line installation convenient, neatly arranged, protect the wire insulation, and ensure the safety of the car, the entire line on the car (except for the high-voltage line, battery cable, and starter cable) is wrapped into a bundle with cotton yarn or fine PVC tape.

2. The composition of the wiring harness

The wiring harness is composed of wires of different specifications and properties. The main specifications and performance requirements are as follows:

 (1) The cross-sectional area of the wire

The cross-sectional area of the wire should be selected according to the load and current of the electrical equipment. The general principle is that electrical equipment with a long working time can choose 60% of the actual current, and electrical equipment with a short working time can choose between 60% and 100% of the actual current. Between the wires.

 (2) The color of the wire

There are colors and serial numbers on the circuit of the car. With the increase of automotive electrical equipment, the number of conductors is also increasing. In order to facilitate the identification and maintenance of automobile electrical equipment, low-voltage wires in automobile circuits are usually composed of wires of different colors. Color letter codes are marked on the automobile PRZEWOD diagram.

In the car conductor circuit diagram that is generally marked as a color code (represented by one or two letters), the car color of the wire is usually different, and there are two commonly used monochrome and color selection principles. Such as red (R), black (B), white (W), green (G), yellow (Y), black and white (BW), red and yellow (RY). The former is the color line, and the latter complements the color.

 (3) The physical properties of wires

① Bending, the metal wire between the door and the door body should be made of well-bent metal wire.

② Wires are used for high-temperature and high-temperature parts, generally, vinyl chloride and polyethylene-coated wires with good insulation and heat resistance.

③Shielding performance. In recent years, electromagnetic wave shielding circuits using weak signal lines have also increased.

 (4) Bandage of wire harness

①Use semi-folding packaging, painting, drying, and other processes to improve the strength and insulation performance of the cable.

② A new type of wire harness, partly wrapped in plastic, is placed in the side-cut plastic corrugated pipe, making it stronger, more protective, and easier to find fault lines.

3. Automotive wiring harness fault type

①Natural damage

　The use of the wire harness exceeds the service life, which causes the wire to age, the insulation layer is broken, and the mechanical strength is significantly reduced, resulting in a short circuit between the wires, disconnection, and accumulation of iron cores. The wiring harness terminal is oxidized and deformed, resulting in poor contact, which will cause the electrical equipment to fail to work normally.

②Electrical failure causes damage to the wiring harness

　When overload, short circuit, and ground fault occur in electrical equipment, it can cause damage to the wiring harness.

③ Human fault

     When assembling or repairing auto parts, metal objects crush the wire harness and break the wire harness insulation; the improper position of the wire harness; wrong connection of the lead position of the electrical equipment; reverse connection of the positive and negative leads of the battery; The electrical equipment operates abnormally and even burns the wiring harness.

4. Inspection method of automobile wiring harness

①Visual inspection

    When a part of the vehicle's electrical system fails, there will be abnormal phenomena such as smoke, sparks, abnormal noise, burnt smell, and heat. By listening to the senses, touch, and smell of the body, seeing the car's wiring harness and electrical visual inspection, and then determining the location of the fault, the detection speed is greatly improved. For example, when the car line fails, there are often abnormal phenomena such as smoke, sparks, abnormal noise, burnt smell, and heat. Through visual inspection, components can quickly determine the nature of the fault and the fault lies.

② Instrument inspection method

    Use comprehensive fault diagnosis instrument, multimeter, oscilloscope, current clamp, and other instruments to diagnose automobile circuit faults. For electronic control system cars, generally use fault diagnosis instrument to find fault code to diagnose the measured fault range; then use a multimeter, current clamp, or an oscilloscope to check the voltage, resistance, current, or waveform of the relevant circuit, and diagnose the fault point of the wiring harness.

③Tool inspection method

   The test lamp inspection method is more suitable for short-circuit fault conditions, check the line. It should be noted that when using the temporary test lamp test method, the lamp power is not too high, in particular, whether there should be careful and whether there is enough output in the output terminal of the test control output of the electronic controller, the controller is used to prevent overload damage. Diode lamps are again preferred.

④Check method of jumper

   The jump connection method is to use wires to connect the suspected faulty line, observe the change of the meter pointer or the working condition of the electrical equipment, and then determine whether the line is open or poorly connected. Cross-connection refers to the operation of connecting two points in the circuit with a wire. The potential difference between the two points is zero, and there is no short circuit.

⑤Repair of wiring harness

   For wiring harness with minor mechanical damage in obvious insulation damage, short circuit, loose wiring, rusty or broken wire connector, a repair can be used; for wiring harness fault repair, the root cause of the failure should be completely eliminated, and the failure should be eliminated again The reoccurrence is usually due to the rubbing of the wire and the impact of the metal part due to the root cause.

⑥ Replacement of wiring harness

    For wire harness aging, serious damage, internal circuit short circuit or internal circuit open circuit failure, it is usually necessary to replace the wire harness.

1. Check the quality of the wiring harness before replacing the wiring harness.In order to ensure the safety and reliability of the wiring harness, it must be strictly controlled before use. It should be inspected with a qualified certificate. If defects are found, it must not be used to prevent harm caused by unqualified products.. Under conditions, it is best to use an instrument Inspection of.

Let includes checking: whether the wiring harness is damaged, deformed, corroded or has no terminal, the connector of the connector itself, whether it is a short circuit between the bad wiring harness connector and the wiring harness, and short circuit conditions. Testing tools are essential.

2. Do not replace the wiring harness until all the electrical equipment on the car fails.

3. Harness replacement steps.

      (1) Harness disassembly tool prepared.

　　(2) Remove the battery of the malfunctioning vehicle.

　　(3) Disconnect the connectors of the electrical equipment connected to the wiring harness.

　　(4) Make a record of the whole process.

　　(5) Loosen the wire harness and fix it.

　　(6) Disassemble the old wire harness and assemble the new wire harness.

4. Verify the correctness of the connection to the new harness. Connecting the wiring harness connector and the electrical equipment is the first confirmation, and it also ensures that the positive and negative connections of the battery are correct.

During the inspection process, it can show that there is no wire connected to the battery, and use a bulb (12v, 20w) to test the bulb. Before that, other electrical equipment is turned off to the car, and then the negative pole between the battery and the frame is connected with a test light. Once there is a problem with the circuit, the test light starts to brighten.

When the circuit fails, remove the bulb and connect a 30A fuse in series between the negative pole of the battery and the frame end. Do not start the engine at this time, check the corresponding power supply equipment on the car one by one, and check the related lines one by one.

5. The test of power supply work. If there is no problem with the responsibilities associated with the electrical equipment and the circuit, the fuse can be removed, the battery ground wire is connected, and the power is tested.

6. Check the wiring harness installation. Ideally, check that the wiring harness is installed correctly and safely.

Although the hidden dangers of automobile wiring harness faults are great, as long as the actual situation of automobile maintenance work is combined with the careful study and application of modern technical means and methods, there are still rules for fault diagnosis; similarly, in the maintenance and replacement of wiring harnesses, it is necessary to strengthen research and continuously improve the maintenance standards. , To ensure safe and reliable automotive application maintenance.