Many industry professionals use the terms “cable assembly” and “wire harness” interchangeably. However, while these components may have similar basic functions, they are distinct products designed for different environments and each require their own methods of troubleshooting.
Wire harnesses consist of multiple wires or cables contained within a simple exterior sheath. The sheath is typically made from thermoplastic or thermoset, which provides a small degree of environmental protection to the conductors. However, since these assemblies generally serve as a low-cost organization solution for electrical systems, it usually does not provide a significant amount of protection against strong damaging forces like friction and temperature fluctuations. As a result, wire harnesses are often not suitable for use in demanding environments.
Similar to wire harnesses, cable assemblies consist of multiple wires or cables covered by an exterior sheath. However, the sheath is made from more heavy-duty materials, such as thermoplastic rubber, shrink-wrapped thermoplastic, or vinyl. This rugged construction enables it to withstand extreme environmental conditions, which helps keep the conductors safe from abrasion, compression, friction, heat, moisture, and other potentially damaging forces.
While wire harnesses and cable assemblies are engineered for different applications, both play a critical role in electrical and electronic devices and systems. However, both can experience various issues that stop them from working as intended or as expected. Below, we highlight some of the most common problems that occur in cable assemblies and wire harnesses and how to avoid or resolve them in this convenient troubleshooting guide.
Problems may arise in cable assemblies and wire harnesses that affect their performance. Developing an understanding (and eventual troubleshooting) of these problems—including what causes them, what signs they exhibit, and how to avoid/resolve them—is essential to preventing expensive repair or replacement issues down the line.
Some of the most common problems that occur in cable assemblies include:
- Inappropriate cable selection — The cables or wires chosen for a cable assembly should be appropriate for the application and/or environment. Otherwise, they may misperform, underperform, or fail during operation. For example, the cables and wires should be durable enough to withstand a reasonable amount of force within the given application and environment. If they are too weak, they may lose connection or break. A pull test helps determine and/or verify the strength of an assembly.
- Incorrect installation — The cables, wires, and other assembly components must be installed properly. If they are installed incorrectly, they can sustain damage that affects their performance. For example, if the technician sets the die incorrectly, it can cause imbalanced pressure, which can lead to a poor crimp and cause deterioration over time. If the technician sloppily solders the connection, they can leave behind buildup that can interfere with connectivity.
- Improper testing — After a cable component is assembled, it should undergo testing to ensure everything was connected correctly and is working properly. Improper testing can lead to missed assembly issues that can cause bigger problems in the future.
- Micro-fretting — Oxidation can form when certain metals are in contact, particularly tin and lead. Intact plating can prevent issues in low-voltage applications.
Some of the most common problems that occur in wire harnesses include:
- Incorrect wire preparation — The wire preparation stage includes selecting the wire, cutting it to the right length, and stripping its ends. While this can be done manually or automatically, errors (human or machine) can occur that lead to incorrectly prepared components.
- Improper layout — After the wires are fully prepped, they must be properly arranged to fit into the harness. Form boards can help identify issues like missing or misplaced wires.
- Inadequate labeling — Improper labeling frequently occurs with mass-produced harnesses. Producing sample labels with the work order can help prevent this issue.
- Crimping and/or soldering defects — Both improper crimping and soldering can lead to circuit issues. That’s why it is important to use the right equipment and technique for the assembly process.
- Wrong or missing components — A side effect of rushed production is quality issues, such as forgotten wires or incorrect hardware. Both can lead to wire harness failure during operation. Double-checking the assembly documentation can help avoid these problems.
- Inappropriate wire tying technique — The final assembly step is tying the wires. If the manufacturer ties the wires too tightly, they can damage them. If they tie the wires too loosely, the assembly may fall apart.
In cable assemblies and wire harnesses, issues can be constant or intermittent. Constant issues are noticeable at all times. Intermittent issues are noticeable sometimes. The latter are much harder to detect and resolve.
Three of the most common errors in cable assemblies and wire harnesses are opens, shorts, and miswires. As intermittent issues, they can have a number of causes, such as:
- Bad setup: the value is set such that it allows the cable to only pass intermittently
- Weak contact: the contact was moved before the solder set, resulting in a weakened contact
- Improperly seated pin: the pin is not seated correctly in the connector
- Damaged housing/insulation: the wires or housing are damaged
- Worn contacts: the contacts on the interface cables are worn
- Dirty contacts: the contacts have residue buildup
Despite the best efforts of the manufacturer, issues and errors can still occur in cable assemblies and wire harnesses. That’s why testing the components after they’ve been built is important in an effort for proper troubleshooting. The procedures verify that they are assembled properly and working correctly. Some of the commonly performed tests include mechanical testing, environmental testing, electrical testing, visual testing, and signal integrity testing.
Mechanical tests assess the mechanical properties of the cable assembly or wire harness, determining whether or not they can meet the application requirements. Typical properties tested include elongation, flexibility, tensile strength, crush resistance, impact resistance, and cycles to failure.
Environmental tests assess where the cable assembly or wire harness can withstand the environmental conditions with the application. Some of the conditions often evaluated during production or troubleshooting include humidity, salt spray, temperature, and vibration.
Electrical tests assess the electrical performance of the cable assembly or wire harness, verifying whether or not they are configured properly and performing correctly. The three things to test for are open wires, incorrect wiring, and shorting risk. The easiest way to check for all three issues is by connecting the assembly to an electrical fixture.
Visual tests assess whether or not all components are present in the cable assembly or wire harness and if they are in good condition. Some of the things to check when performing visual tests are:
- The wires/cables for the gauge, the placement, and potential damage
- The connectors/terminals for the proper types
- The labeling for accuracy and placement
It is also important to test the dimensions to ensure the assembly is up to spec.
Signal integrity tests assess the strength of the signals the cable assembly or wire harness can carry. Some of the elements they look at include signal error and crosstalk. They also check whether the signal strength can be maintained with the integration of connectors, filters, or splices.
Many problems may arise in cable assemblies and wire harnesses. While having a personal understanding of each of their causes is essential for troubleshooting, partnering with an experienced cable assembly and wire harness manufacturer can facilitate the resolution process.
For a partner you can trust for all of your custom cable assembly and wire harness needs, turn to the experts at Carr Manufacturing! We have extensive experience designing and delivering high-quality, competitively priced custom wire and cable assemblies for various industries and applications. To learn more about our capabilities or for assistance in troubleshooting your product, check out our project gallery or contact us today.