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What is an automotive wiring harness and its function?

What is an automotive wiring harness?

An automotive wiring harness is the main network of electrical circuits in a car.  Without a wiring harness, automotive electrical circuits would not exist.  A wiring harness refers to a component that is made by punching contact terminals (connectors) from copper material, and then insulating them with molded insulation or adding an external metal shell, forming a bundled assembly of connected circuits.

In simple terms, an automotive wiring harness assembles cables, connectors, terminals, and wires to transmit electrical power within a vehicle.

In the past, cars were purely mechanical and could operate without electricity.  However, driving a modern car without electricity would be a miracle.

Therefore, automotive wiring harnesses are crucial components for any car’s engine.  Without them, the current cannot reach the various electrical components of the vehicle.

The ignition systems of cars, such as the starter, chassis, and alternator, all require electrical power.  Without automotive wiring harnesses to transmit them, they would not receive this power.

However, having just an automotive wiring harness is not enough for a car.  The wires and terminals must also be correctly connected to the electrical components.

Understanding these connections is essential in understanding different wiring harness circuits.

Automotive Wiring Harness Circuits

Since automotive wiring harnesses connect to different electrical components, they have various wiring circuits.These circuits serve different purposes. A standard conventional automotive circuit consists of eleven:

Dashboard illumination lights、Instrument cluster、Turn signals、Heating and air conditioning、Horn、Parking lights、Radio broadcasting、Brake lights、Tail lights、Turn signals、Windshield wipers

From their names, you can easily understand the function of each circuit.

However, many high-end vehicles’ wiring harnesses have more than 12 circuits. Some have 18, while others have 24. These additional circuits are important because the vehicles are equipped with more electrical components.

If a car has 18 circuits, you would find the following as additional circuits:

Electric fuel pump
Electric fan
High-mount stop lamp
Two power locks
Radio B+ memory

But if a car has 24 circuits, in addition to the 18 mentioned above, the following are extra circuits:

Dome light
Trunk light
Glove box light
Clock
Engine compartment light

Components of an automotive wiring harness

In addition to circuits, an automotive wiring harness consists of various components, including:

Connectors

Connectors, as the name suggests, are used to connect the wiring harness wires to different circuits and power sources. Typical connectors have male and female terminals that are connected together to transmit electrical current.

However, the type of connectors varies depending on the wiring harness. Their terminals also come in different materials, with brass and copper being the preferred options.

Fuses

Fuses, in general, serve to protect electrical components in case of faults, such as when there is excessive current flow.

Wiring harness fuses are characterized by wires that are designed to easily melt at a certain current level. When they melt, the circuit is broken.

Thus, they can prevent random currents from reaching the vehicle’s electrical components, protecting them.

Fuse box

Each circuit in a wiring harness has an individual fuse. This means that if one fuse fails, it doesn’t affect all the components. The fuse box is like a house where you can assemble different fuses. It is similar to a distribution board.

Relays

Relay components in an automotive wiring harness are used for high-current circuits. It is one of the essential components that directly draws power from the battery. In contrast, some components derive power from other automotive system components. Therefore, relay components can transmit powerful currents from low-current sources.

Wires

The harness is composed of cables or wires. Cables or wires are the components seen here. These are typically copper wires with variations in circuit measurements.

For example, the horn and headlight circuits use 1.5mm² wires. However, the circuits for dome lights and door lights use 0.5mm² wire. When purchasing wires for circuits, confirming the circuit’s current value is crucial.

 

 

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