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HomeTips & GuidesWire Harness Terminals: A Detailed Guide About Different Types of Terminals

Wire Harness Terminals: A Detailed Guide About Different Types of Terminals

In any electric system, you use terminals to connect wires to any equipment. You may need them either while installing new connectors or replacing old broken ones. Along with terminals, you will also need proper tools for efficient installation of these tools. The most common tools used are wire crimpers. 

In this blogpost, you will learn about wire harness terminals. 

What are wire harness terminals?

When you connect any conductor to a chassis, stud, post or other piece of equipment, the devices you need for terminating are known as terminals. 

Among so many varieties of terminals, a few to name are spade, ring, bullet, quick-disconnect, hook, flagged and butt terminals. 

Also, insulated and non-insulated options are available. Insulated wire terminals have a protective covering that acts as a non-conductor.

A wire terminal’s insulation can be nylon, heat-shrink or vinyl. The wire remains protected from water, moisture, heat and cold.

However, insulated terminals can cost a bit more. On the contrary, non-insulated options are more economical than insulated ones. You can use them when your application does not require extra protection. 

Which wire terminals will be the best for your applications depends on the usage. Whichever you pick must meet your project requirements and industry standards. 

Terminal crimped colorful electric wire.

Terminal crimped colorful electric wire.

Types of wire harness terminals:

Wire harness terminals come in different shapes and sizes based on the size of the wire and the screw. 

Ring terminals:

In ring-type terminals, there is a round end which allows easy connection with any stud or screw. You can also call them ring connectors in insulated and non-insulated versions. As these ring terminals come in different sizes, it is essential that when you choose a ring terminal, it must match your wire gauge size and stud size. You can either crimp or solder this terminal. 

Spade terminals:

Also known as space connectors, spade terminals come in different sizes. Thus, you must consider the right wire size and stud size while choosing it.

Due to its open end, the spade terminals are quite convenient to attach or remove from a screw. Available in insulated and uninsulated versions, these terminals are suitable for electrical systems with tight installation spaces. 

Hook terminals:

Hook terminals are similar to spade terminals, as they also have open ends. For the same reasons, they are convenient to use in installation. These terminals are also available in insulated and non-insulated versions and offer durable connections for different projects.

Quick disconnect terminals:

With quick disconnect terminals, you can easily connect/disconnect two wires. These terminals are commonly available in industrial, auto and consumer products as they offer durable and stable connections. In these terminals also, you can choose from insulated and non-insulated versions.

Bullet terminals:

Bullet terminals or bullet connectors offer reliable, secure and easy connection. They can also be easily disconnected. These terminals easily connect with open-ended round female and male connectors, setting a highly durable connection.

Bullet terminals are quite sturdy as they prevent wire harnesses from corroding and entering harmful materials.

Butt terminals:

With butt terminals, you can terminate either single or multiple wires. As these terminals prevent cutting and abrasion, they help remove corrosion, moisture and any other negative elements in the harness.

Butt terminals allow easy extension of wires as they fail to connect themselves. To use butt terminals, put each wire on the connector’s open end, crimp both ends and secure the connection.

Flagged terminals:

Flagged terminals or flag connectors offer easy and secure connections. They are suitable for connections in tight spaces. It offers quick disconnection as well. You can choose from insulated and non-insulated varieties.

Types of wire harness terminal insulations available

The insulation on the wire terminals makes them resistant to different environmental conditions, extending their overall life. The major insulation types are:

Heat shrink:

Due to its various advantages, it is a popular choice among insulation materials. Firstly, its epoxy covering prevents moisture ingression in the conductor, thus protecting it from corrosion.

This type of terminal is very useful for marine applications. Also, due to their abrasion-resistant nature and high flexibility, they have a longer life than other insulation options.

Further, as they are translucent, you can check your crimp connection and ensure it is strong.

Nylon terminals:

It’s a double-crimped terminal, as one crimp occurs on the wire while the second crimp on insulation strengthens it. Due to this, the connector has a strong hold and long life. Also, they are semi-translucent, so like heat shrink, you can visually verify the crimp connection of the wire.

Vinyl terminals:

These are the most effective insulation types. Available in different styles, these connectors are the most common choice in insulated terminals.

Non-insulation wire terminals

There is no insulation in non-insulation wire terminals, so they do not offer any protection. However, they are cost-effective and easy to inspect. If you find any connection loose, you can add solder to strengthen it.

Automotive wiring harness with positive battery terminal for generator

Automotive wiring harness with positive battery terminal for generator

Steps for wire harness terminal crimping process:

Here are 5 steps that help you understand the wire crimping process from start to finish.

Choosing the wire:

You must know the equipment’s requirements to choose the right type of wire. Find the wire size, often mentioned in AWG or American Wire Gauge. If you fail to find this information, you can still determine the wire size. Take the equipment wire and cut a small length of insulation. Now, count the number of wires and determine the diameter of one wire strand. Based on this, multiply the diameter of one wire strand with the total number of strands.

Select the crimp terminals:

The terminal you choose will also determine the quality of the crimp. You should consider these points while selecting a terminal:

  • Try to choose terminals with plating as they have low contact resistance and offer corrosion protection.
  • Pre-insulated terminals come with a metal sleeve, which helps to grip the wire properly. If possible, choose pre-insulated terminals.
  • Made using rod materials, these terminals are round in shape and support connector creation.

Determining the crimping tool:

Crimping tools come in several designs. However, you must pick one that is compatible with your crimp terminal. Look for the tooling information on the manufacturer’s website. If information is unavailable, pick a tool that shows compatibility with the crimp terminal. Choosing the right terminal ensures a firm crimping.

Making the crimp:

You must follow these steps for the crimping process:

  • First, determine the length of the wire to be crimped and strip off its insulation. Ensure that you crimp the wire to a length so that when you insert it into the crimp, 1-2 mm of wire must protrude. Cut off the insulation to expose the wire strands.
  • Now, insert the wire into the crimp, taking care that all strands move inside the crimp.
  • Put the wire and the crimp into the crimping tool and seat them there perfectly. Now, rotate the crimping tool until it is released.
  • Finally, remove the crimp and check the wire. It should be in the right position. To ensure that wire and crimp are properly secured, give a tug to it.

If using heat shrink:

Slide the sleeve onto the crimp and the wire, making sure that it does not cover the terminal end of the crimp. Once you place the sleeve in the right position, use a hot air gun to shrink the heat shrink tubing.


Cloom has a wide range of options. We provide four types of insulation, including nylon, vinyl, heat shrink and non-insulated. You can choose the wire terminals to serve the needs of your multiple applications from these different options. We ensure that all our products meet industry compliance and regulatory standards.

Contact us for detailed information regarding wire terminals.

I am Lillian Yang, having been a sales manager for over 10 years.

I have received many positive reviews from customers. They have praised our excellent service, on-time delivery, and high-quality cable assemblies.

For your projects, please provide cable assembly files/images/smples, etc., so that I can send you a quotation within 24 hours.

Contact me now and let’s get started on building your wire harnesses!

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