We usually divide automobile wiring harnesses into front cabin wiring harness assembly, engine wiring harness assembly, gearbox wiring harness assembly, instrument wiring harness assembly, indoor wiring harness assembly, door wiring harness assembly (four doors are different), ceiling wiring harness assembly, rear trunk wiring harness assembly, battery positive and negative wiring harness assembly, airbag wiring harness assembly and other parts. In order to achieve a simple structure and easy disassembly and assembly of specific vehicle models, modular designs will be used in the wire harnesses as much as possible to reduce loops and will not stick to these classifications.

Front cabin wiring harness assembly

The front cabin wiring harness is in the harshest environment, with many parts and components and a relatively small space. Therefore, when arranging the front cabin wiring harness, factors such as waterproofing, heating and vibration must be fully considered to protect and fix the wiring harness.

Main electrical components in the front cabin: powertrain and its accessories (currently there are few models with rear-mounted engines), ABS system, lamps, wiper and washing system, power supply system, central electrical box (some models are also placed indoors) ) and some other electrical devices.
Automotive powertrain wiring harness

The automotive powertrain wiring harness is also located in the front compartment, including the engine wiring harness and transmission wiring harness.

There are many sensors and actuators on the automobile powertrain. It is necessary to fully consider the positional relationship of these sensors and use fixed points on the powertrain or use fixed points on it to design brackets to fix the wiring harness.

The electrical components of the powertrain are mainly the sensors and actuators on it, including crankshaft position sensor, phase sensor, vehicle speed sensor, knock sensor, water temperature sensor, oil temperature sensor, electronic throttle, speed control valve, carbon canister solenoid valve , ignition coil, fuel injector, EGR, CBR, eddy current control valve, high-pressure oil pump, pressure temperature sensor, boost pressure sensor, position switch, reverse switch, etc. 
Instrument panel wiring harness assembly

The instrument panel concentrates most of the operating switches and display devices of the entire vehicle, and gathers multiple control units. At the same time, the wiring harness docking parts are often designed on both sides of the instrument panel. Therefore, the instrument panel wiring harness is one of the most complex wiring harnesses in the entire vehicle. 

In the instrument panel, there are mainly the following electrical components: HVAC, audio system, airbag, instrument electrical box, BCM, ECU, TCU, brake switch, electronic accelerator pedal, clutch switch, cigarette lighter, backup power supply and various switches parts (such as combination switch, alarm switch, etc.).

Indoor wiring harness assembly

The indoor (floor) wiring harness is the longest and largest wiring harness in the entire vehicle. It runs through the entire body and is the first wiring harness to be considered in the design of the entire vehicle. 

There are relatively few electrical components in the indoor wiring harness, such as electric seats and heating, electronic oil pumps, seat belt switches, rear wheel speed sensors, corner sensors, etc., but their locations are relatively scattered.
Door wiring harness assembly

The door wiring harness (different for four doors) is relatively small, and there are relatively few issues to consider, mainly the door's movement mechanism, door rubber parts and fixation.

The main electrical components of the door wiring harness are glass lift switches and motors, electric rearview mirrors, horns, door locks, latches, threshold lights, side turn signals, child safety switches, etc.

Other wiring harnesses

In addition to the above wire harnesses, there are still some other smaller wire harnesses on the vehicle, such as battery positive and negative wire harnesses, rear defrost positive and negative wire harnesses, ceiling wire harnesses, airbag wire harnesses, rear cover wire harnesses, etc.

These smaller wiring harnesses usually have the following electrical components: battery, airbag, rear defroster, license plate light, dome light, sunroof, trunk switch, etc.

Battery positive and negative wire harness assembly: The battery, starter, generator and ground are connected by the battery positive and negative wire harness. The current passing through it is the largest, which can exceed several hundred amperes. 

Ceiling harness assembly: The main electrical devices connected to it are ceiling lights, skylights, vanity mirror lights and other electrical devices. 

Airbag wiring harness assembly: It mainly connects the electrical components of the airbag, mainly considering the reliability of the connection, such as terminal gold plating.

Rear trunk wiring harness assembly: The main connections are the license plate light, rear door latch and other electrical components. 

Haiyan ADS Special Cable Co.,Ltd manufactures kinds of wire to fit automotive wiring harness. For instance, xlpe wires like TXL, SXL,GXL,  pvc wires like AVSS, GPT, AVS, Teflon wires like UL1332 etc.