What To Look For In A High Quality Wiring Harness

custom wiring harness is designed to save you time, money and improve project efficiency.

But what goes into making a high quality wiring harness? It’s not just the outside, but the inside of the cabling you need consider.

If you’re thinking about getting a custom built harness, you want to be sure that the manufacturer is going to build you something that will last and function properly.

Not all cables are created equal, so here’s 6 key components to look for in a high quality harness.

#1 – Quality Of The Conductor

A good place to start is to check what the conductor is made out of, whether it’s a:

  • Steel conductor which is clad in copper
  • Aluminium conductor which is clad in copper
  • Fully copper conductor

A fully copper conductor is the highest performing choice as it has the lowest resistance and the highest conductivity.

You’ll also need to check that the wire gauge (thickness) is adequate.  It is vital to ensure that the wire is robust and wide enough to safely carry the required amount of electrical current along the length of the wire.

Determining the right wire gauge will be dependent on the intended usage and the length of the wire – you don’t want to over spec or under spec.

#2 Solid Vs Stranded Wire

Deciding on the right type of wire core is conditional on the application the wiring harness needs to perform. If the wrong type of core is being used, the wiring won’t perform optimally.

Stranded wiring has increased flexibility compared to solid wiring. Stranded wires are best to use when the wire needs to be moved frequently over short distances such as in a pair of headphone cables or in a patch cable. In a custom wiring harness, you would opt for stranded wire when the harness needs to threaded around and into tight spaces. Stranded wire allows for a greater bend radius to be easier to install.

Solid wires are more appropriate when the wiring does not have to be moved often and doesn’t require a small bend radius, such as routing cables through walls or in ceiling cavities. Solid wires have less resistance per 100 feet compared to a stranded wire, making them a better electrical conductor. If a solid wire is bent, or flexed, too many times, the wire will experience metal fatigue and possible failure.

# 3 Robustness Of The Outer Sheathing

At first glance, a wiring harness might LOOK like it’s built to last, however there’s a number of factors to consider in determining whether the wiring will be able to withstand its anticipated usage.

Strain relief (or bend relief) is fundamental to contributing to the overall robustness of the outer sheathing of a cable and preventing the conductor from breaking. Proper strain relief will also stop any load applied to the cable from being transferred to the conductor terminations.

Another aspect to consider is whether the strain relief is moulded or field installable and which is more suitable for your application.

Furthermore, there’s a whole plethora of ratings that increase the robustness of a cable. Depending on the application of the wiring, look for the following ratings as an indication of the quality of the wire harness.

  • Chemical resistant
  • UV rated
  • Fire retardant
  • LSZH (Low Smoke Zero Halogen)
  • Plenum (rated for cavities used for air circulation)

Armoured ratings such as Steel Wired Armour (SWA) and Aluminium Wired Amour (AWA) may also be necessary depending on the intended application of the wires, especially when it comes to underground and hazardous environment applications.


# 4 Reputable Connector Brand

You can be looking at a beautifully made wire harness with great performance and specs, but if the connectors aren’t up to scratch, then you are going to have a weak link.

While there are basic industry standards to be adhered to, some manufacturers offering cheaper offerings may not have equipment with close tolerances, quality raw materials or stringent quality control measures. So the end result may be connectors that fail, or are at best, niggly and difficult to use. This is especially a concern when there is a high mating cycle (repeated unplugging/plugging).

The best way to avoid this is to only use reputable and trusted connector brands such as Molex, Amphenol, Lemo, Belden, TE Connectivity, etc. That way you can be totally confident the wiring will perform properly.

# 5 Fully Certified

A harness is of little use to anyone if it doesn’t carry the right industry certifications.

If all the components of the harness have been sourced from a fully certified manufacturer, then you can be rest assured that the wiring is of excellent quality and will perform reliably.

But it’s important to note that different industries, such as medical, mining and communications, all require different certifications.

The military in particular has its own set of unique certifications in order to guarantee all equipment being used is extremely heavy duty and reliable. In fact, many heavy duty cables and connectors are often graded as “Mil-Spec” (Military Specification) even if they are not intended for military use. Mil-Spec helps to achieve interoperability, ensures products meet specific requirements, commonality of parts, increased reliability, lowers total cost of ownership, compatibility with logistics systems, and similar defence-related objectives.

There are also unique certifications for wiring used in hazardous environments and some certifications incorporate IP(Ingress Protection) ratings for dust and waterproofing.

Another consideration to remember is that different countries may have different certification requirements within the same industry. For example, the auto industry in the USA has very different wiring certifications compared to the Australian auto industry.

Ensuring that a wire harness meets all necessary certifications is also important for ensuring there is full traceability.

# 6 Tried And Tested

At the very minimum, a wire harness should be tested by the manufacturer for continuity and polarity.

Testing the electrical polarity (positive and negative) means testing that the direction of the current flow in an electrical circuit has been connected the right way. If the manufacturer hasn’t connected the electrical polarity of a wire harness correctly, it can result in damage to the equipment it is connected to.

A continuity test is completed using specialist test equipment to ensure that an electrical circuit is completely closed and not open. The test will help to identify breaks or issues in the flow of current and ensure that connections are correct between two, or more, points.

A high quality harness manufacturer will have the proper testing equipment to test all connections at the same time and ensure no mistakes are ever made.

In fact, the best manufacturers will not only conduct tests on prototype harnesses, but they will test EVERY individual harness before they go out the door.

Be sure to check the testing standards of any harness manufacturer and ask for copies of testing records so you can be completely confident in their product.

To Wrap Things Up

So as we’ve discovered, there are a lot of factors that go into making a high quality custom wiring harness.

What makes up both the internal and the external of a harness is key to how well it will perform in the context of its intended usage.

If your wiring and cables needs have got you tangled up, call the experts at QCC Custom Cables.

Our team have the expertise and access to the right equipment to deliver a workable solution for you, in full and on time.

For more information and advice, simply click here to get in touch.