The on-board harness is also called low-voltage harness. The harness is copper multi-core flexible wire circuit. The common specifications are 0.5, 0.75, 1.0, 1.5, 2.0, 2.5, 4.0, 6.0mm2, etc. The key is to look at the current value of the load. Different power consumers are equipped with different specifications of wires.

1. On-board harness. The main harness of the whole vehicle is usually composed of engine (ignition, electronic injection, power generation, starting), instrument, lighting, air conditioning, auxiliary electrical appliances, etc. According to the purpose, location and function of the main harness, there are many branch on-board harnesses. The main harness of the whole vehicle is centered on the instrument panel, extending from front to back, and covering the whole vehicle. Generally, it can be divided into head harness (including instrument, engine, headlight assembly, air conditioner and battery), tail harness (tail lamp assembly, license plate lamp, high-mounted brake lamp and trunk lamp), roof harness (door, ceiling lamp and loudspeaker), etc.

2. Car air conditioning harness. Take the whole vehicle harness as an example: 0.5mm2 specification line is used for instrument lamp, instigator lamp, door lamp, ceiling lamp, etc; 0.75mm2 specification line is applicable to license plate lamp, front and rear small lamp, system, etc; 1.0mm specification line is applicable to turn signal lamp, fog lamp, etc; 1.5mm specification line is applicable to headlights, horns, etc; The specification line above 10mm is a practical idea.

3. Car switch harness. In order to facilitate identification and error correction, each end of the on-board harness is usually marked with a number and letter to indicate the connection object of the wire. When the operator sees the mark on the harness, he can correctly connect to the corresponding wire and electrical equipment. This mark is convenient for repairing or replacing the harness. In addition, using the same wire color to distinguish the same circuit is also a simple sign.

4. Car lamp harness. According to the location of the vehicle harness, the information and binding methods used are also different: the engine harness usually has to go through a long time of high temperature, wind and sun, rain, stable strength and other special environments. Due to the harsh working environment, the design uses a high flame retardant, waterproof, high mechanical strength threaded tube to wrap separately. The working environment of the front cabin line of the car is also poor. Most branches are wrapped with threaded pipes with good flame retardance, and some branches are wrapped with PVC pipes. The working space of the instrument line is small and the environment is good, so the method of full tape wrapping or flower wrapping is adopted. The working space of the door line and the ceiling line is small, so they can be completely wrapped with tape, and local branches can be wrapped with industrial plastic cloth; The thinner roof line can be directly attached to the vehicle with sponge tape. Because the chassis wire has a lot of contact parts with the body, it is wrapped with ripple tubes to avoid harness wear.