How to Prevent Failure in Complex Electrical Assemblies


Electrical assemblies used in manufacturing come in all shapes and sizes — from circuitry in small electronics to expansive and complex configurations for avionics and heavy duty vehicles. The more complex, the greater the risk of failure.

If an electrical failure occurs in a heavy duty vehicle used for a military operation or on an airplane at cruising altitude, the consequences can be catastrophic. While failure analysis can be conducted and reveal issues, preventing failure in the first place is always the goal of any engineer or designer.

When designing complex electrical assemblies, there are several areas of consideration that need to be addressed to ensure reliable results, quality products, and the safety of those who use them.

Thermal Conditions

Extreme temperature fluctuations are one of the greatest threats to electrical assembly performance, especially for equipment that undergoes repeated and prolonged use. In a vehicle, for example, wiring that runs through an exhaust system or engine compartment must withstand high temperature spikes. Thermal failure can result in cracking, breakage, coefficient thermal expansion (CTE), contraction, loss of insulation and, ultimately, the loss of power throughput. Determining proper insulation, sleeving, shielding and routing are critical to protect wires exposed to excessive thermal conditions.

Chemical Exposure

Electrical wiring and components need to be protected from chemicals that can cause corrosion. Without proper protection, wires can be exposed to hydraulic oil, diesel fuel, coolant, grease, dirt and other abrasive elements. In the case of a fire truck, consider that the unit will likely be exposed to soot, ash, smoke, flying debris and off-gassing from any nearby fires. These conditions and chemicals can quickly break down improper insulation and expose wiring, resulting in the potential ignition of surrounding combustible materials. Proper housing, seals, insulation, routing and materials must be used.


Excessive moisture can also cause corrosion and dangerous conditions. Consider if your design will be exposed to moisture, such as road spray, a pressure washer or submerged in water for periods of time. The wiring must be protected from the corrosive effects of humidity under these conditions. Once again, the type of housing and insulation used are critical to ensure terminals are properly sealed.


Designing the configuration of complex wire harnesses and assemblies brings many challenges. An assembly may need to span a wide expanse, such as in the fuselage of an airplane, or it may need to fit within tight constraints, such as behind an already congested vehicle dashboard. Both require proper length and tensioning to prevent wire fatigue, pinching, arching and a host of other failures.


Choosing a proper covering can help minimize the effects of vibration on an electrical assembly by providing proper insulation, but proper routing is of equal importance. When configuring a wire harness, make sure it will not rest on a surface exposed to excessive vibration, causing insulation breakdown, chaffing and an eventual electrical fault. Select materials that are less rigid and prone to cracking under stress.

Design Analysis

Without question, proper design is at the root of most failure prevention and can mitigate the risks mentioned previously. Working with engineers with expertise in designing electrical assemblies may be your greatest tool in ensuring reliability. With their in-depth knowledge and experience, they can more easily and quickly identify potential problems and recommend different component selections, reconfigurations of wire routing, materials, housings, and more.

They’ll also be familiar with mandatory regulatory requirements for various industries and can ensure compliance. As part of the design phase, prototyping and testing are conducted for system validation and to reveal improvement opportunities. Special software can also be used to predict potential failures and design for reliability. Take full advantage of collaboration opportunities with your supplier’s engineers and designers to ensure reliable performance of your electrical assembly components.

If a failure occurs, it’s rarely the wire that’s the problem; rather, it’s a result of the external abuses and environmental conditions it’s exposed to. Selecting the right wire for the right application is still a critical element, but the routing, testing and overall design remain equally important.

If you’re looking for a partner that can perfect your product and mitigate the risks associated with its electrical assemblies, reach out to us here at MCL. We’re ready to tackle your toughest manufacturing challenge with innovative technicians, cutting edge technology and a no-fail attitude!


Questions to Ask Before Designing an Electrical Assembly for Heavy Duty Vehicles


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