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Posted by Rick Regole on August 19, 2019 | Updated on November 18, 2019

Picture of a Wiring Harness If a wiring harness fails, causing a short or open circuit, technicians can face a real headache or worse – a full-blown catastrophe. Just imagine if the wiring harness at fault was delivering mission-critical power to a safety sensor or engine. What if the short sparked a fire? In transportation, where thousands of lives are at stake every day, it’s vital to understand what causes a wiring harness to go bad, and how to engineer around risks.

Wiring harnesses fail in four key areas:

  • The Cable
  • The Fixturing
  • The Tester
  • The Technician

Here are the top four reasons why:

1. Poor Design

Wiring harnesses are not a one-size-fits-all apparatus. A machine usually cuts the wiring to length and strips the ends to prepare for crimping the wire with a terminal. If the machine isn’t properly maintained or adjusted, user error can cause mistakes, including improper wire layout, poor connection to the harness chassis, or inexact measurements that prevent the entire wiring harness from fitting correctly inside the application. If wires are not laid out according to the application specs, they may not connect to the harness chassis or fit into the finished product.

Depending on the complexity of the wiring harness, a wire or piece of hardware can also easily get missed or misplaced.

2. Incompatible Components

If the wiring size is not correct for the amps and wattage, the harness can overheat. Unfortunately, advances such as the use of modern halogen versus standard incandescent lights can cause compatibility problems that inexperienced technicians may miss.

3. Low-Quality Material

Copper alloy is a cheap alternative to OEM-grade copper for wiring and terminals. However, this type of material is prone to overheating and breaking under repeated stress. Likewise, the protective jacketing and overmolding material must be compatible with environmental factors, like exposure to oil and grease, chemicals, extreme temperatures, etc. If the overmolding is not resistant to these elements, it can melt, corrode, become brittle, crack, and expose wires.

4. Defective Crimping or Soldering

Any time an electrical joint is present, there’s a risk. Crimping is the most common type of bond used to attach wires to terminals. When crimps are not done properly it can lead to short circuits or open circuits within the product. Or, the crimp could spontaneously fail, even if it passed a functional test. Regardless of whether you are hand crimping or using a machine, it is important to ensure equipment is set up correctly for the size of wire you are crimping. If it is performed by an inexperienced technician or used in instances where soldering should have been used, the crimp might not be secure and could shake loose. Crimps are also more susceptible to overheating. In applications that involve movement or exposure to vibration, soldering the wires to terminals forms a stronger, more reliable bond. However, a soldered joint can also have issues — if the temperature is too hot or too cold, or the soldering gun tip is not the correct size.

If you suspect an issue with your wiring harness, or if you are in the process of designing a new harness for your product, work with an original manufacturer like iCONN Systems. We are a top-tier designer and manufacturer of custom connectors and cable assemblies, with the experience and expertise to help you build or replace your wiring harness with confidence.

For more advice on selecting the right electrical components, download our free buyer’s guide: How to Get the Best Connector for Your Project.

Buyer's Guide iCONN Systems

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