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Is Crimping The Auto Harness Wire OK?

Is crimping the auto harness wire OK? Yes, easy and quick, crimping makes a reliable join, which creates microscopic welds between wires. 

However, it would be best to have the right crimping tools and crimp connectors to make a perfect joint. 

Fortunately, a selection of crimp connectors and crimping tools are not expensive. 

Keep reading to find out how to achieve a successful crimping.

Table of Contents

Different types of crimping connectors

Crimp connectors come in various sizes, accommodating up to the largest wiring AWG.

Seam vs. seamless connectors

Seamless connectors

Simply put, these connectors are cut from the round stock, making them tube-like.

Seam-type connectors

These connectors are cut from the flat stock and then rolled into a shape similar to a tube to have a seam running the entire connection length. 

The seam can be difficult to see through the connector’s insulation. However, you can essentially look at the end to tell the connector type you have.

When you crimp a seamed connector, ensure the seam is not opened. You can easily accomplish this by verifying if the seam is opposite the stake and perpendicular to the tool.

Non-insulated crimp connectors vs. Insulated crimp connectors

Non-insulated crimp connectors

A non-insulated crimp connector does not have insulation. Therefore, it should be appropriately insulated once you have crimped it in place, essentially using heat-shrink tubing

The trick is to choose an insulation that perfectly fits both the connector OD and the wire’s gauge you crimp onto.

Non-insulated connectors come in various forms, from seam or seamless to ring terminals to butt connectors. 

Insulated crimp connectors

The insulated crimp connector is the most popular among all the mechanical connectors. 

Similar to the non-insulated connectors, the type comes in different sizes and types with nylon or vinyl insulation, flared or straight. Further, flared end connectors provide higher chances of a perfect fit.

The insulated crimp connectors are our preferred choice as they save time because you won’t need to insulate your connector once you finish crimping. 

Heat-shrinkable insulated connectors

These connectors offer exceptional insulation and connection. Think of heat-shrink insulation as combining a crimp connector with heat-shrinkable insulation around them.

You can utilize heat-shrinkable insulated crimp connectors one time, and it isn’t easy to go back to anything else. However, they are costly.

The mechanics of using these heat-shrinkable connectors are similar to the distinctive insulated connectors. 

However, the insulation is heat-shrinkable to offer a waterproof connection, ideal for underneath the vehicle, under the hood, or even for marine use.

Non-insulated seam-type terminals

Non-insulated seam-type terminals

Different shapes of crimp connectors

Butt crimp connectors

These types of crimp connectors are among the most common types of crimp connectors and are perfect for making end-to-end or butt connections between two cables. 

They come in up to 8 AWG. You can even get larger sizes on request.

Ring terminal crimp connectors

These are the second most popular types of crimp connectors. 

They are a helpful option whenever you terminate a wire to a point of connection, like a bolt or stud on the back of an alternator.

They are also extensively handy in terminating a wire to the ground.

Ring terminals come in different diameters, including those as large as your available wire.

Fork or spade terminals

The fork terminals are popular as they allow you to terminate your wire to a point of connection and offer an easy connection to that particular point.

Unlike ring terminals, which need you to remove a nut from the stud or bolt you want to connect to make the connection, a spade terminal lets you simply loosen that particular stud or bolt and slide your terminal underneath.

It is particularly useful when connecting to a barrier strip using several connections.

Quick disconnect crimp connectors

We have used these types of connectors a lot because we try our best to consider serviceability when adding a circuit to any automotive. 

A perfect example is mounting a light or switch in a removable dash panel. The quick-disconnect connector on the light or switch lets you quickly remove the panel.

So, instead of your dealer cutting the wiring when servicing your car, they only need to unplug the panel.

There are two types of quick disconnect connectors, which are both available in female and male versions:

  • Push-on crimp connectors
  • Butt connectors

With 4+ wires, a female or male plug is the right way to do things.

The quick disconnect connectors are ideal for low-current applications under the hood or car.

Insulated wire crimp connectors

Insulated wire crimp connectors

Right crimping tool for the job

When using top-quality crimping connectors, your stake won’t tear or pierce the insulation.

Non-staked crimping tools

A non-stake tool is any crimping tool with a radiused, smooth surface on the two sides, such as the one on the connector/crimper set.

They are “squeeze-type” crimping tools that won’t give you adequate leverage to make high-quality crimps. They have a relatively narrow contact surface.

Squeeze-type crimping tools 

Squeeze-type crimping tools 

Traditional staked crimping tools

It refers to any crimping tool with a half-round surface on one jaw’s side and a stake or point on the other.

They are what professionals use since they provide excellent leverage and make perfect crimps. 

They are also available in multiple sizes, handled up to around 8 AWG.

The majority of stake tools come with a minimum of two openings. You need to pick the opening that best suits the connector you are crimping. 

When properly picked, it will not deform your connector, and the stake seats the connector fully on your wire without destroying the copper.

Staked crimping tools

Staked crimping tools

Handheld compound action crimping tools

A compound crimping tool is no more complex than a handheld crimp tool. However, when you crimp big connectors, you must apply more force to complete the job correctly.

They offer higher leverage and can crimp up to 4 AWG non-insulated or 8 AWG insulated connectors. 

However, handheld compound cation crimping tools are hard to fit into tight spaces.

There are two methods to crimp large gauge wire connections properly. Both methods need a special tool to complete the job correctly. 

  • A hammer-type crimp tool (a cheaper method). 
  • A hexagonal compound crimp tool (an expensive method).

Crimping wire auto harnesses

Most experts, including us at Cloom, prefer a perfect stake-type crimp tool for non-insulated and insulated connectors. 

How to crimp non-insulated ring terminals

  • Strip off around ¼ inch of insulation from your wire’s end.
  • Twist the wire’s stripped end clockwise to ensure all the wire strands can be easily inserted into the connector’s ferrule.
  • Push your ring terminal over the bare wire’s end, ensuring that the whole of your wire is inside the connector’s ferrule (only a minimum of 1/16 inch of your wire should be sticking out of the other bare wire’s end).
  • Orient your crimping tool around your ring terminal, ensuring your stake is opposite the seam. (optional)
  • Completely squeeze the crimp tool to make the crimp.
  • Once crimped, grasp your connector and twitch it slightly to ensure it is correctly seated on your wire. If you don’t crimp the wire properly, it will come right off.

How to crimp insulated butt terminals

  • Strip from both wires around ¼ inch of insulation.
  • Twist the wires’ stripped ends clockwise.
  • Insert your first wire into your crimp connector, ensuring the copper fully fits into your ferrule and your wire’s insulation perfectly fits into the vinyl or nylon.
  • Orient your crimping tool around your butt connector’s half that the wire is within.
  • Fully squeeze the crimp tool to make the crimp.
  • Repeat the above steps for the other half of your connection.

Whenever you crimp seamless butts, you should reverse your crimp tool’s orientation for every crimp. 

That allows one stake to be on both sides of your connector. It also makes the butt connection straight and nice. If you take both on one side, the butt will typically end up curved slightly.

Conversely, when you crimp a seamed butt connector, ensure the stake will often be exactly opposite your seam. The two stakes should be on one (same) side of your connector.

How to crimp heat-shrinkable insulated connectors

This option is the same as crimping discussed above but with one additional step.

For instance, once you have properly crimped the insulated connector, heat it using a heat gun until the heat-shrinkable insulation surrounds your connection.

Crimping large AWG wire connectors

As mentioned above, you can use two methods to connect outside the vehicle. Therefore, you need to plan accordingly.

Using a hammer crimp tool

  • Strip off the right amount of insulation from the wire using a razor blade. That varies depending on the connector you are crimping onto your wire. However, you will always want around ⅛ inch of the wire popping out at the end of any huge open connector’s ferrule.
  • Push your ring terminal over the bare wire’s end, ensuring all of your wire is in the ferrule. It would be best if you had at least ⅛ of your wire sticking out of the opposite end of your bare wire.
  • With your crimping tool on a flat, hard surface, insert the connector or wire into the crimping tool. Make sure the stake is directly opposite the seam.
  • Using a hammer, firmly drive the stake into your ring terminal. It typically requires only 1-2 whacks from a large hammer to have the job done correctly. However, it would be best to remember that when you hammer excessively, the stake will tear through the connector’s bottom, damaging the crimp integrity.

Using the hexagonal compound tool

  • Put the dies on the jaws for the connector AWG you use. (The color-coded jaws correlate with a chart on the hexagonal compound crimping tool itself).
  • Strip off the right amount of insulation from your wire using a razor blade. These can vary depending on the connector you are crimping onto your wire. However, it would be best if you aimed for around ⅛ of your wire popping out of any open ferrule connector.
  • Open the tool’s jaws and hold the tool fully by one handle. Rest the free handle on the floor. Use your free hand to insert the ring/cable terminal into the tool’s jaws, ensuring the seam of your connector is at the center of one of your hex opening’s flat sides.
  • As you start compressing the crimp and the tool, you must let go of the wire and utilize both hands to compress the crimp tool fully.

Depending on the length of your connector’s ferrule, you may need a second similar crimp directly next to your first crimp. That should be considered before you make the first crimp.


We hope you know it is OK to crimp an auto-wiring harness. However, to achieve a perfect crimp, you should use high-quality terminals and crimping tools. 

Fortunately, Cloom offers customers superior quality and affordable wire harnesses and cable assemblies to suit your specifications and needs.

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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