With the increasing demands of people on the safety, comfort and economy of automobiles, there are more and more electric devices and functions on automobiles, soAutomotive wiring harnessIt is also becoming more and more complex and has become a frequently-occurring link of contemporary automobile failures, and therefore has received more and more attention in automobile design and manufacturing. What is the design process of the car?

　　
1、 Schematic design and calculation
1. The electrical schematic diagram shall be drawn according to the electrical configuration and technical requirements in the Electrical Design Assignment.
2. The fuse capacity and wire diameter shall be determined according to the power of each electrical appliance, and the load distribution shall be carried out for each electrical subsystem to determine the total fuse capacity.
3. Calculate wire diameter:
According to the formula:
I -- current, A;
P -- power of electrical components, W;
U -- voltage, V;
A - wire diameter, mm2;
ρ——— Copper resistivity (about 0.0185 Ω mm2/m);
L=conductor length, m;
Ud - maximum allowable voltage drop loss.
　　
The following situations should also be considered:
1. The wire diameter can be appropriately enlarged if the wire is too long;
2. When the wire is connected to the consumer after being connected by multiple connectors, the wire diameter can be appropriately enlarged considering the large terminal voltage drop.
3. Different types of conductors have different allowable current and line voltage drop.

2、 Draw cable and harness diagram:
1. According to the different positions of various electrical components, determine the form of 3D wiring. At present, the commonly used wiring forms in the world are generally E type and H type;
2. Simulate the harness diameter in different areas;
3. Consider the sealing and protection of harness vias.
4. The fixing hole position and fixing form of the harness shall be determined.
5. Theoretically, it is the most reasonable to connect all electrical components with one wire harness, but it is impossible to do so in actual loading. Therefore, the wire harness should be reasonably divided into blocks, and systematic design should be adopted as far as possible in the case of convenient assembly.
6. The grounding point design is very important in the wiring harness design, otherwise it will cause signal interference and affect the function realization of some electrical appliances; Multiple grounding points shall be designed according to different vehicle types, and the grounding design shall meet the following requirements: a. The weak signal sensor shall be grounded separately and nearby to ensure normal signal transmission; B. Each ECU shall be grounded separately to prevent interference; C. The negative grounding of the battery and the grounding of the engine and transmission should be carefully considered.

3、 Design 2D harness diagram
　　
1. The distribution box (fuse and relay) is the core of the whole vehicle electrical system, which plays the role of distributing load, centralized power supply, saving space, simplifying wiring harness, reducing cost and facilitating maintenance. Generally, it can be designed into 2 to 3 as required. The distribution box of some newly developed models has the function of electronic control; And the central control box without contact and fuse will also have more and more market, and Tongjie is at the forefront.
　　
2. The color of wires shall be selected according to ZBT35002 Color of Low-voltage Wire for Automobile.
　　
3. Selection of connector:
1) Select connector according to wire diameter and passing current;
2) The engine compartment adopts sealed connectors;
3) The connector with double-spring compression structure is preferred to reduce contact resistance.
　　
4. Harness binding method:
1) The cab is generally wrapped with tape at intervals;
2) The instrument panel is generally wrapped tightly with adhesive tape;
3) The parts on the floor or far away from the engine are generally wrapped with flame-retardant bellows;
4) The interior of the door and trunk door is generally wrapped with adhesive tape or industrial plastic cloth;
5) Some areas close to the engine are wrapped with insulating glass fiber sleeves or wire harnesses.

In addition to the above, attention should also be paid to:Automotive wiring harnessThe distance between the anti-theft ECU and the read-write coil to prevent signal transmission attenuation; All electrical components for signal transmission, such as "oxygen sensor", "knock sensor", "read and write coil", shall be LE-SE signal wire or shielded wire.