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HomeTips & GuidesButt connection Vs. Solder on automotive wire harness: To crimp or to solder? That’s a question.

Butt connection Vs. Solder on automotive wire harness: To crimp or to solder? That’s a question.

Butt connection Vs. Solder on automotive wire harness: There are several ways to connect wires in automotive wire harnesses. But the main problem is where you should go for heat shrinking, soldering, butt connectors?

People often believe butt connectors are better for power and ground wires than soldering and heat shrinking, as soldering makes the wires stiff and prone to breakage during vibrations.

So, which is better for vehicles – butt connector vs. solder on automotive wire harness? And for a third option, can heat shrink be used over the butt connectors?

Let’s find out in this article.

Table of Contents

Butt connector vs. solder on automotive wire harness: The basics

The primary reason for the problems in the electrical connection is faulty connections in wires and cables.

 Most applications use crimp terminals as they are reliable and efficient. However, it can develop corrosion over time, leading to issues in the connection.

 Another reliable method to repair electronic devices is soldering.

Butt connector:

In the butt connection, you use a splice connector, which is a simple cylindrical connector having crimps at both ends. 

This is the most common and helpful connector in electrical applications. It’s a crimp connector that helps terminate wires safely and connect them. 

  • For this, you need to insert the wires into the connector. 
  • Next, crimp the connector with the help of pliers, resulting in bending and deformation of the connector around the wire. 
  • The crimping force also physically connects the wires and the connector’s metal. 
  • Last, you can also repeat the same process at the other end.

Solder on automotive wire harness:

Soldering is a traditional way of terminating wires. You use a molten metal, solder, to form a reliable and strong connection between wires, cables, or any other electrical components. The metal solder can be anything of silver, brass, or tin. 

  • Heat the metal to a temperature above 600 degrees Fahrenheit with a soldering iron. 
  • Then, join the two components with hot molten metal.
  • Finally,  let it cool down.
Solder on automotive wire harness

Solder on automotive wire harness

Butt connectors vs. Solder on automotive wire harness: The pros and The cons

Though both butt connector and soldering help connect wires, the butt splice connector is better than soldering. Let’s find out how.

keysButt connectionSolder connection
ProsThis method is also simple, affordable, and accessible; no complex tooling is required. You only had only flux and the solder.
The soldering connection is resistant to corrosion.
For crimping, you need to be very careful and require specific tools, while soldering is preferable when you are down the road and lack time for that.
This method is also simple, affordable, and accessible; no complex tooling is required. You only had flux and the solder.
The soldering connection is resistant to corrosion.
For crimping, you need to be very careful and require specific tools, while soldering is preferable when you are down the road and lack time for that.
ConsCrimping requires specific tools, which may be expensive. 
Further, wrongly performed crimping can damage the connector or lead to faulty connections.
If the crimped connection fails, you need to replace the complete assembly of the connector. 
You cannot re-crimp or re-install a faulty connection.
It is labor intensive, and one has to be careful while soldering wires.
Soldering is less practical for adverse environmental conditions as soldering often fails during extreme temperature and mechanical conditions. 
Also, vibration can make the flux stiffen over time, damaging electrical connections.
If solder does not melt properly during connection, it can lead to a rough, inconsistent surface, weakening the connections.
Some non-RoHS (Restriction of Hazardous Substances) solder preparations comprise lead, which may lead to fumes and dust.

Butt connection Vs. Solder on automotive wire harness: Applications

In the aerospace and automotive industries, you need reliable and robust connections. 

The crimped wires create a cold weld, whose pressure leads to the formation of metal and its oxide layers at the micro level. 

Thus, butt splice connectors are the most reliable and efficient wire connection method.

On the contrary, you can use soldering to connect wires and terminals in low-current and delicate applications like circuit boards in electronics. 

However, if your car is down on the road, you may prefer soldering the wires to crimping since they seem to be the proper method of handling.

Automotive wire harnesses

Automotive wire harnesses

Is it helpful to heat-shrink butt connectors?

Sometimes, engineers also use heat shrink to seal the butt connector ends, which results in the contraction at the end, locking the wires and butt splice connectors and making them weather resistant.

Heat shrinks are a unique insulation that shrinks on applying heat, which usually has an adhesive. 

 If you see an opaque plastic insulator, don’t mistake it for a heat shrink connector, as it will melt on applying heat.

These connectors are preferable for all wiring applications in trucks, cars, boats, trailers, campers, and other vehicles. 

You can use these butt splice connectors with heat shrink for repairing wire damages caused due to rodents, corrosion, and other reasons. 

Whether for temporary or permanent repairs, the connection is reliable and long-lasting. 

Another good thing about heat shrink insulation is that they are color-coded for the intended wire gauges.

heat-shrink butt connectors

heat-shrink butt connectors

Tools required for heat-shrink connectors:

You need the following tools, along with the heat-shrink connectors, to make a firm connection.


There are several types of crimping tools and crimp-on wire connectors. 

Thus, it is essential to choose a suitable crimper; otherwise, it can deform the metal, damage the insulation, make a wrong crimp connection, or lead to all three together.

Wire stripper:

Before crimping, you must strip off the wire insulation for about 3.16 of an inch. An automatic wire stripper makes the work easier and faster but is costly.  

If you don’t want to invest in it, a simple, inexpensive wire stripper will also do.

Heat gun:

You want a source for flames to provide heat to the insulation but don’t just bring a cigarette lighter or anything like that. Heat guns provide heat in a controlled manner and are worth an investment.

The right way of using heat-shrink connectors:

  • First, take a wire stripper and strip the wire to the length of the connector’s barrel.
  • Now, twist the conductor ends slightly so they do not unravel while inserting them into the connector.
  • If using a butt splice connector, examine the metal barrel’s seam. If the crimper’s male jaw has a convex surface, put the crimping tool’s female jaw over the seam. On the contrary, if the crimper contains flat jaws, out the seam against any jaw but not sideways.
  • Further, if you use fork, ring, or hook terminals, put the seam in a way so that it remains at the top when you mount the terminal.
  • Adjust the connector barrel in the tool and the ratchet to hold the connector and not bend or crimp it.
  • Put the wire in the connector barrel and crimp the connection with a crimping tool. Ratchet-type connectors release only when the barrel crimps completely.
  • Lastly, use a heat shrink to insulate the connection. The heat shrinking will provide weather resistance and structural rigidity to the joint.


So, weigh the pros and cons according to the applications when deciding on the connection. 

Always remember that your priority should be the quality of the connection. 

Cloom is here to clarify your doubts regarding crimping or soldering. We have years of experience implementing different custom wire harnesses and cable assembly types.

Hi I am Christa, sales manager of Cloom.

I have extensive expertise and experience in wiring harnesses and I believe I can help you.

And we have a very professional technical team who can clearly understand the customer’s needs and give professional suggestions and solutions after receiving the drawings.

If you also have wiring harness needs, please send me the drawing so that we can give you our quote and start our business.

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