Wire HarnessWire Harness Designing

Selection of Terminals in Wire Harness Design

Selection of terminals is one of the important aspects in wire harness designing process. Electrical wire harness is the nervous system of any automobile. It is our normal experience that cables and wires are difficult to organize. Where as keeping them straight is another challenge. Wire harness assembly can keep cables better organized and help the automobile run smoothly. Without wire harness there is possibility that wire can cross each other. Crossing the wrong wires could fry the entire system. Hence, knowing right wire going at right place with the proper protection can help keep things run smoothly.

Wire Harness

Wire harness assemblies are almost like a universal language among professionals. Molex, TycoJST, Terminal Technology are the international supplier of connector and terminals which follow world class standards. So if an electrician installs a wire harness assembly in an automobile and a different electrician comes by later. Then they will know what’s going on as the process is same. Automobiles run in various environments where things can get very hot like Rajasthan or very cold like Ladakh. In such situation the right wire harness assembly will keep the contents inside safe. In every such condition the main aim of harness is to supply power uninterruptedly.

Terminals and Crimping

If we talk about terminals. They are defined as a device which are designed to terminate a conductor that is to be affixed to a post, stud, chassis, another tongue to establish an electrical connection. Wire Terminals come in many different shapes and sizes depending on the size of the wire and screw. Several types of terminals include ring, blade, hook, quick-disconnect, bullet, joint, button, earth terminals and flagged. Wire terminals are available in insulated and non-insulated. Determining the best fit depends on the application and design parameters.

Once the proper terminal is selected according to current carrying capacity, ambient temperature etc. Then cables are crimped into the terminal. In wire harness manufacturing process crimping and crimping strength is a crucial parameter.  Crimping technology has been developed to replace the need to solder terminations. This technology provides a high-quality connection between terminal and wires at relatively low applied cost.

Selection of Terminals

Once the wire harness design engineer select proper connector for harness, the next step is to select the terminals. Following points can come handy while selection of terminals.

  • Compatibility with the connector:

    Terminal selected must be compatible with the connector used.

  • Wire size range:

    The selected terminal must be crimped on the required wire size with the crimping standard to be met.

  • Application:

    Before selecting the terminal application must be carefully seen.  Weather you are using terminal in high temperature zone or not. As well as in  high power applications or low power application. For high temperature zone tin plated terminal is preferred against brass terminal. Higher series terminals to be used for high power application and lower series for low power and signal application.

  • Conductivity:

    Terminal provides electrical contact between wire and mating parts. Hence the contact resistance is very important. The contact surface areas maybe brass, tin, silver or gold plated. It should be selected depending upon the sensitivity required. For the terminals used as signal application gold plated terminals may be required for high sensitivity like for air bag sensors. For finalizing terminal always customer should provide the permissible contact resistance.

  • Retention Force:

    The retention force between the two mating terminal should always be considered in case if housing to housing lock is not present. Positive lock terminals to be used if high retention force is required.


  • Eyelet terminal should be opted as per current rating and bolt diameter in the vehicle.
  • From the data of a load of a particular unit, establish the wire size and type that is to be used.
  • If the customer has specified any particular terminal or connector, the same has to be used.
  • If the customer has not specified any particular terminal or connector, select the terminal for suitable wire size and current carrying capacity.

In next part we will see terminal selection based on series, tab size and current carrying capacity.


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