Four Ways to Prevent Wiring Harness Failure

By Rick Regole | March 11, 2025

Wiring harnesses save installation time, optimize space, and help protect circuits from shock, vibration, debris, and other hazardous conditions. Good decisions at the design stage can protect the harness and the application.

Wiring harnesses save installation time, optimize space, and help secure and protect electrical circuits from shock, vibration, debris, and other hazardous conditions. Also called cable harnesses, these bundles of wires are a critical design strategy that can build efficiency into an application in which multiple systems operate.

For instance, vehicles, which have a multitude of complex electrical and mechanical systems packaged in close proximity to each other, depend on wire harnesses to manage the vast amount of cabling that supports lighting, climate controls, sensor systems, and drivetrain functions. However, the failure of a wiring harness can threaten the safety and operations of an application. One loose wire can leave a short or open circuit. A faulty wiring harness tasked with delivering mission-critical power to a safety sensor or engine can have catastrophic implications. What if the short sparked a fire? In applications such as transportation, automobiles, or medical devices, lives are at stake and it’s vital to understand what causes a wiring harness to go bad, and how to engineer around risks to protect the application. Problems with wire harnesses begin in the cable, the fixturing, the tester, or the technician. Designers can prevent those problems by paying special attention in four key areas.

Design dependability into a wire harness

Wire harnesses are not one-size-fits-all. Problems can start at the design or manufacturing stage. To make a harness, 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.

Skilled assemblers, as well as well-maintained and tested precision equipment, are essential. Make sure your supplier is up to date with the latest equipment, technology, and testing needed to design and create dependable wire products.

Wire Harness

Specify interconnects for compatibility

Make sure that every element in a wiring harness properly supports the design. Specifying compatible interconnects, including wire and cable, connectors, sensors, and antennas, helps ensure optimal performance and longevity. Otherwise, problems with one component can affect others. For example, if the wiring size is not correct for the amps and wattage, the harness can overheat. Consider the end application the wire harness supports to make sure the components meet the performance requirements. Advances such as the use of modern halogen versus standard incandescent lights, for instance, can cause compatibility problems that inexperienced technicians may miss.

Choose quality

Quality components should be specified for every part of a wiring harness to optimize performance and longevity. 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. The higher quality option delivers higher levels of performance. Likewise, the protective jacketing and overmolding material used to bind and secure the wires must be compatible with the environmental factors the harness will be exposed to in the application, such as surface oil and grease, chemicals, and extreme temperatures. If the overmolding is not resistant to these elements, it can melt, corrode, become brittle, crack, and expose wires.

Prevent crimping or soldering problems

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.

Consider every aspect of the application to design, assemble, and install a successful, safe, and durable wiring harness. Specify quality materials, components, and assembly practices every step of the way to avoid issues with your wiring harness. Work with an original manufacturer of custom connectors and cable assemblies with the experience and expertise to help you build or replace your wiring harness with confidence.

Visit iCONN Systems to learn more about selecting the right electrical components for your application and download our free buyer’s guide, How to Get the Best Connector for Your Project.