Ji Jin is a professional engaged in various types of plastic mold design, manufacture and injection molding processing of production-oriented enterprises.
The composition of automobile wiring harness
First of all, let's take a look at the composition of the automobile wiring harness, which consists of wires, terminals, sheaths, tapes, PVC pipes, corrugated pipes, waterproof heat-shrinkable tubes, and some auxiliary materials, such as packaging, protective materials, etc., which are the connections in the circuit. Wiring parts of various electrical equipment. In order to facilitate the installation and later maintenance, the wires of different specifications and colors used by the electrical equipment of the vehicle are generally arranged into bundles reasonably, and the wires are bundled with insulating materials.
There are also rules for the color selection of automobile wiring harness wires, which is convenient for later maintenance. The wires are of different colors. At the same time, the cross-sectional area of the wires will be marked before the color code. The color of the wires is clearly marked in the installation drawing of the automobile wiring harness. replication is very important. And the choice of wire color is a single color is preferred, followed by two colors. In addition, in the car wiring harness installation diagram, the ground wire of various automotive electrical appliances should be black wires, and the black wires have no other purpose except for grounding. The color of the wire is indicated by the color code, such as a single-color wire, the color is green, marked as G, a two-color wire, the ** color is the main color, the second color is the auxiliary color, the main color is green, and the auxiliary color is white. for GW.
The cross-sectional area of the wires of the electrical equipment on the car determines the size of the load current. If it is an electrical appliance with a particularly small current, such as an indicator light circuit, the cross-sectional area of the wire should be greater than 0.5mm2, which can better ensure the due mechanical strength. The working time of electrical equipment also determines the actual current carrying capacity of the wire. Electrical equipment that works for a long time can use 60% of the actual current carrying capacity of the wire, and electrical equipment that works for a short time can use 60%-100% of the actual current carrying capacity of the wire. It is worth noting that when the cross-sectional area of the wire is in millimeters, it can be left unmarked. For example, 1.25G means a green wire with a wire cross-sectional area of 1.25mm2.
Causes of car wiring harness failures
Common car wiring harness faults are poor contact of connectors, short circuit, short circuit, grounding, etc. between wires. These common failure causes are divided into two types: natural factors and human factors.
natural factors
The automobile wiring harness has exceeded its service life, the wires are aging, and the insulating layer is damaged, resulting in short circuits, open circuits and grounding between circuits, thereby burning the wiring harness. In most cases, the failure of electrical equipment to work is caused by poor contact, and a large part of the reason is that the wiring harness terminals are oxidized and deformed.
Human Factors
When assembling or repairing auto parts in the later stage, the metal object scratches the wiring harness and breaks the insulating layer; the wiring harness is not in the proper position, and the remaining space is too large or too small; the lead position of the electrical equipment is connected incorrectly; the positive and negative electrodes of the battery are connected reversely; during the maintenance When there is a problem with the circuit, connect or cut the wires randomly. These factors will affect the electrical equipment, and even burn out the wiring harness.
How to find out the fault point of the car wiring harness
Cars sometimes have various problems, so how do we judge which link is wrong? To solve the fault, we must find a specific short-circuit point, and we need to check the entire electronic system circuit, but this is cumbersome and workload. big thing. The automotive electronic system supports many functions, and the wiring harness of the system is relatively complex. The wiring harness of the whole vehicle is composed of trunk roads and several branch circuits, and dozens of sensors, electrical appliances, and switching elements are set on it. It is very difficult to find a short-circuited point from such a complex and huge system.
Since it is so complicated and time-consuming to check for car wiring faults, isn't there a simple and quick method? The electrical appliances in the car are generally grounded by the sound of the car, which means that the circuit flows from the positive electrode of the battery to the electrical appliance, and then flows back to the negative electrode of the battery or through the body. It flows back to the negative terminal of the battery as a loop. In the event of a short circuit, the current will not pass through the electrical appliance and flow directly from the body back to the negative pole to form a short circuit. In order to avoid large losses in the wiring harness line after a short circuit fault, most live wires will be equipped with fuses, which are used to short circuit the wiring harness lines. is to cut off the line. When the car wiring harness is short-circuited, generally we use a test light to connect to the positive pole of the battery. If there is a fault, the test light will be lit. But at this time, we can't observe the current flow inside the wiring harness. The current sensing clamp is a good sensing tool.