Wire HarnessWire Harness DesigningWire Harness Manufacturing

Wire Harness Components Wire, Protection & Material You need to Know

Wire harness are the integral part as well as act as nervous system of every automobile. Like two-wheeler, three-wheeler, every car, truck, passenger vehicles, commercial equipment and even in military vehicles. As the nervous system is the back bone for the human’s every day living, the same is true for wire harness in automobiles.

In this article we will discuss about each and every component that is used in functioning wire harness. Wire harness consists of wires, connectors, terminals, fuses, relays, corrugated tubes, sleeves, grommets, clamps, clips, cable tie, ferrule, heat shrink tube, seals, tapes etc. Failure or defect in any of this component can damage the performance of your automobile. Hence these components are designed and selected carefully according to standard defined by automotive industry all over the world.


Wire harness is a bundle of wires tied together. Main purpose of these wires is to carry power and transfer signals to various electrical components in automobile. Such as electronic control, cluster, headlamp, power windows, electric starter motor and doors etc in the vehicle. There are many types of wires or cables are used in road and vehicle application. Along with this some cable varieties are more flexible, more heat resistant or more cold resistant. Some are smaller thickness for easier routing or larger for products requiring more current.


The main role of connector or coupler is to connect wires or cables within an automobile. It provides necessary fitment and insulation for terminal to hold inside it. Connector in automobile can come in contact with water, harsh environment, extreme temperature variations, vibrations, electromagnetic interference and various conditions. Hence, they are designed considering every such possibilities. Nowadays, with increased use of information technology, variety of connectors that connect wires to GPS, TV, and other wave receiving devices are being developed for automobiles.


Terminals are the current-carrying connection points between the wires and the various application in the automobile. They are made of a variety of metals, these parts can be coated differently to meet a number of conditions. Terminals get fix inside the connector or can be directly attached to devices depending on the design of application in any vehicle.


Fuses are circuit protection devices to protect  the circuits in any electrical system. Automotive fuses are a class of fuses used to protect other components, devices, and wiring from any damage. This might occur due to excess current flow. They are generally rated for circuits no higher than 32 volts direct current, but some types are rated for 42-volt electrical systems. Fuses are primarily identified by an amperage rating. This rating refers to the maximum amount of amperage that the fuse can handle before it fails. Automotive fuses are typically contained within fuse boxes.


Automotive relays of all shapes and sizes can be found in every automobiles. Relays in general are used to enable a low amperage circuit to switch on or off a higher amperage circuit. Like starting the electrical starter motor in two-wheeler.  If you were to try and directly hook up your starter motor to the self start switch. Then, you would exceed the amperage rating of the switch. Hence will result in melting of switch, wires, and risk of an electrical fire. Relays are also used to switch multiple things at the same time using one output. 

Corrugated Tube

Corrugated tubes are bendable, heat resistant, strong in clod climate, and available in various size and color. Wire harness design point of view these features provide necessary protection to bundle of cables. Corrugated tube has many spiral projections on the inner and outer surface of the tube. Extra turbulence generated due to the spiral grooves results in a substantial increases in the heat transfer. Corrugated tubes are generally made out of thin walled tubes in various ferrous and non ferrous material.


Sleeves avoid any damage to cable. It even avoids the penetration of water, chemical compounds and protect from harsh environment. It helps to protect from fire spread. Some of the features of sleeves are,

  • High Strength
  • Excellent Longevity
  • Optimum Finish
  • Low Maintenance
  • Affordable costing


A grommet fits externally to a wire harness to be wired in a vehicle. If a wiring harness to be routed through a hole of vehicle body then rubber grommets should be used for protection of the harness. The grommet has a small-diameter cylindrical portion molded of elastomer, through which the wire harness is tightly inserted. Grommets can also be used for water proofing of the harness if sealing agent is provided below it. Grommets can withstand set resistance, tear and heat resilience, fire resistance. They possesses resistance to chemical and salt sprays.

Typical harness grommets include:

  • Wheel house grommets
  • Firewall grommets
  • Door bellow grommets
  • Dash grommets
  • Wiper grommets
  • Front-of-dash grommets

Clamp/Clips and Cable Tie

Supporting clamps provide support and fix up wiring harness on the body firmly. Because of clamping the noise produce due to vibration of wiring harness with body will not occur. Along with this, wire harness clips help keep wire and cable manageable in wire harness assembly. Board retainer clamps help stand-off wire and cable bundles for easier cable tie application.

Cable tie are used to tie the wires in automobile at specific location. Vehicle running on road constantly vibrates. In this vibration or sudden jerk, cable tie hold the wire harness at its desired location. For those applications where strength, vibration, weathering, extreme temperatures and corrosion are present, stainless steel cable ties are ideal.

Electrical Wire Ferrule

Most ferrules consist of a circular clamp used to hold together and attach fibers, wires, or posts, generally by crimping, or otherwise deforming the ferrule to permanently tighten it onto the parts that it holds.An electric wire ferrule is a metal tube crimped over stranded wire to secure the strands within a screw terminal. Electrical insulation may be included to protect any exposed portion of the wire not completely inside the screw terminal post.


Heat Shrink Tube

Heat-shrink tube is a shrinkable plastic tube used to insulate wires. Furthermore, it provides abrasion resistance and environmental protection for stranded and solid wire conductors, connections, joints and terminals. Heat-shrink tubing is made of nylon or polyolefin. It shrinks radially (but not longitudinally) when heated, to between one-half and one-sixth of its diameter. They are rated by its expansion ratio, a comparison of the differences in expansion and recovery rate. It can also be used to repair the insulation on wires or to bundle them together, to protect wires or small parts from minor abrasion.


Wire seals and connector seals of high quality and high precision are made from superior synthetic rubber like Silicon, EPDM, NBR. Wire Harness design engineer select it as per requirement. These seals do not get damaged even in dire environment.


Using tape in wire harness, ensures optimal wire harnessing and protection for automotive applications. They also offer weight savings and reduce harness diameters. Wire harness tapes securely bundle wires and withstand extreme temperatures and environmental conditions. In addition, wire tapes for automotive engine compartments have to be highly resistant to abrasion. Normally many automotive OEMs use wire harnessing tapes made of, PET-fleece, woven, non-woven and film backings combined with high-quality adhesives.


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