Automotive engine wiring harness inspection and wiring harness replacement methods?

Automobile use, wiring harness failure hidden hidden strong, but the fault hazard advantage is very big, especially the wiring harness overheating and wiring harness short circuit failure, very easy to cause a fire. Timely, fast and accurate search for hidden wiring harness faults, reliable repair of faulty wiring harness or correct replacement of the wiring harness is an important work in automobile maintenance, is to prevent automobile fire accidents, to ensure the safe and reliable use of automobile important measures.

First, the function of the automotive wiring harness for easy installation of automotive lines, layout neatly, protect wire insulation, to ensure the safety of automotive use, the car on the car line (high voltage lines, battery cables and starter cables, except) subarea with cotton or thin PVC tape wrapped into a bundle known as the wiring harness, generally divided into the engine wiring harness, chassis wiring harness and the body harness, and so on. Second, the composition of the wiring harness by different specifications of different performance of the wire composition, the main specifications and performance requirements are as follows 1. Wire cross-section according to the size of the load current of the electrical equipment to choose the cross-section of the wire, the general principle of long working hours of electrical equipment can be used to select the actual capacity of 60% of the wire, a short period of time to select the actual flow of electrical equipment can be used to select the actual flow of 60% of the wire -100% of the wire; also should take into account the voltage drop in the circuit, the voltage drop in the circuit, the voltage drop in the circuit and the voltage drop in the circuit. Should also take into account the voltage drop in the circuit and conductor heating and other conditions, so as not to affect the electrical performance of the electrical equipment and the permissible temperature of the wire; in order to ensure a certain degree of mechanical strength, the general cross-sectional area of low-voltage conductor is not less than 1.0mm? 2. The color of the wire automotive circuits are characterized by color and numbering. With the increase in automotive electrical equipment, the number of wires is also increasing, in order to facilitate the identification and overhaul of automotive electrical equipment, automotive circuits in the low-voltage wires are usually made up of different colors, and in the automotive electrical wiring diagrams are marked out with the color of the letter code. In the automotive circuit diagrams are usually marked out the color code of the wire (with one or two letters), the color of the wire on the car is generally different, commonly used single-color and two-color two selection principles. Such as: red (R), black (B), white (W), green (G), yellow (Y), black and white (BW), red and yellow (RY). One of the two-color wire in the first one is the main color, the latter is a secondary color. 3. physical properties of the wire (1) winding performance, the door and across the body between the wire should be composed of a good winding performance of the wire. (2) high-temperature resistance performance, the wire used in high-temperature parts of the general use of insulation and heat resistance of good vinyl chloride, polyethylene-coated wire. (3) shielding performance, in recent years, weak signal circuitry used in electromagnetic shielding wire is also increasing. 4. wire harness wrapping (1) cable half-stacked wrapping method, coated with insulating varnish and drying to increase the strength of the cable and insulation properties. (2) the new wire harness, local plastic wrapping into the side of the cut plastic bellows, so that its strength is higher, better protection performance, find line faults more convenient. Third, the type of automotive wiring harness failure 1. natural damage wiring harness use more than the use of the period, so that the wire aging, insulation layer rupture, a significant decline in mechanical strength, resulting in short circuits between the wires, disconnect, ride, etc., resulting in wire harness burned out. Wire harness terminal oxidation, deformation, resulting in poor contact, etc., will cause the electrical equipment can not work properly. 2. Electrical faults lead to damage to the harness when the electrical equipment overload, short circuit, ride and other faults, may cause damage to the wire harness. 3. man-made faults - assembly or overhaul of automotive parts, metal objects will be the wire harness pressure injury, so that the wire harness insulation rupture; improper location of the wire harness; the leads of electrical equipment The location of the wrong connection; battery positive and negative lead reversal; overhaul circuit failure, messy connection, messy cut wire harness wires, etc., can cause electrical equipment does not work properly, or even burn the wire harness. Fourth, the automotive wiring harness inspection methods 1. intuitive inspection method when a part of the automotive electrical system failure, there will be smoke, sparks, noise, burning odor, high temperature and other abnormal phenomena. Through the human sensory organs of listening, touching, smelling, looking at the automotive wiring harness and electrical appliances for intuitive inspection, and then determine the location of the fault, thereby greatly improving the speed of repair. For example, when the automobile line failure, there will often be smoke, sparks, noise, smell, high temperature and other abnormal phenomena. Through intuitive inspection, can quickly determine the location of the fault and the nature of the fault. 2. instrumentation inspection method using comprehensive fault diagnostic instrument, multimeter, oscilloscope, current clamp and other instruments to diagnose automotive circuit faults. For the electronic control system for cars, the general use of fault diagnostic instrument to find fault codes, to diagnose the measurement of the scope of the fault; and then use a multimeter, current clamp or oscilloscope targeted inspection of the circuit voltage, resistance, current, or waveforms, to diagnose the wiring harness wire failure points. 3. tool inspection method test light inspection method is more suitable for checking the wire short-circuit faults. The use of temporary test light method should pay attention to the power of the test light is not too large, in the test of the electronic controller control output terminals whether the output and whether there is enough output is particularly cautious, to prevent the use of the controller overload damage. ****** use diode test light. 4. conductor across the inspection method across the method that is suspected of having a fault with a wire will be shorted line, observe the meter pointer changes or electrical equipment operating conditions, so as to determine whether there is a break in the circuit or poor contact failure. Cross-connection is the operation of a wire to connect the two points in the circuit, the potential difference between the two points of the circuit across the connection is zero, not a short circuit. Fifth, the repair of the harness for the harness is more obvious at the slight mechanical damage, insulation damage, line short circuit, loose wiring, wire connector corrosion or poor contact can be used to repair the method of repair; harness failure repair, shall completely eliminate the root cause of the failure to eliminate the possibility of failure to re-occur often due to the wire and metal parts of the vibration friction of the root cause of the cause. Sixth, the replacement of the wiring harness for the wiring harness aging, serious damage, internal wire short-circuit or internal wire short-circuit fault, usually have to replace the wiring harness. 1. Replacement of the wiring harness before the harness quality inspection. In order to ensure that the harness is safe and reliable, it must be strictly controlled before use, and should be certified and inspected, and should not be used if defects are found, so as to prevent the hazards caused by unqualified products. Conditions, ****** use instruments to check. Inspection within the let include: wiring harness with or without damage, plug with or without deformation, terminals with or without corrosion, plug itself, wiring harness and plug with or without poor contact, as well as wiring harness with or without short circuit, short circuit. The inspection of the wiring harness is essential. 2. Rectify all the faults of the electrical equipment on the car before replacing the wiring harness. 3. Wiring harness replacement steps. (1) Prepare wiring harness removal tools. (2) Remove the faulty vehicle battery. (3) Disconnect the plugs of the electrical equipment connected to the wiring harness. (4) Make a record of the entire work. (5) Loosen the wiring harness fixing. (6) Remove old wiring harness and assemble new wiring harness. 4. Verify correctness of new wiring harness connections. The correct connection of the wiring harness plug to the electrical equipment is the first thing to be confirmed, and also to ensure that the positive and negative battery connections are correct. When checking, you can show not to connect the battery's hitch wire, instead of using a light bulb (12V, 20W) as a test light. Prior to this, other electrical equipment on the car should be turned off, and then between the negative terminal of the battery and the frame hitch with a test light string connection. As soon as a problem arises in the circuit, the test light will start to turn on. When the circuit of the fault elimination, the light bulb down, with a capacity of 30A fuse connected in series between the negative terminal of the battery and the frame hitch. At this time the engine should not be started, the corresponding power supply equipment on the car one by one to connect, and to the relevant lines one by one comprehensive inspection. 5. Energized working test. If there is no problem with the electrical equipment and related wiring, you can remove the fuse, connect the battery hitch wire, and carry out the energization test. 6. Check the installation of the wiring harness. ****** should check the wiring harness installation to ensure that the wiring harness is installed correctly and firmly. VII. Conclusion Although the hidden nature of automotive wiring harness failure is strong, but as long as the combination of automotive maintenance work, careful research, the application of modern technical means and methods, fault diagnosis is still a rule to follow; similarly, in the work of wiring harness repair and replacement should be strengthened research, and constantly improve the maintenance specifications, to ensure that automotive use and maintenance of safety and reliability.

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