Wiring harnesses are used throughout switchgear, control equipment and safety systems to connect components reliably within an electrical assembly.

Wiring harnesses are used throughout switchgear, control equipment and safety systems to connect components reliably within an electrical assembly.

When a wiring harness fails, the problem is not always immediately obvious. Intermittent connections, damaged insulation, loose terminations or environmental conditions can all affect performance and make faults difficult to identify.

Understanding some of the common causes can help engineers consider both the original manufacture of the harness and its condition during ongoing maintenance.

Here are six areas worth checking.

1. Poor or Damaged Terminations

Reliable terminations are fundamental to any wiring harness.

An incorrectly crimped terminal, damaged conductor or poorly assembled connection can affect electrical performance and, in some circumstances, lead to increased resistance or intermittent faults.

For engineers investigating an existing failure, connectors and termination points are therefore logical areas to inspect for signs of damage, movement, corrosion or overheating.

Good process control during manufacture can help reduce the risk of termination problems. This includes using the correct tooling for the terminal and wire combination, following defined assembly procedures and carrying out appropriate inspection and testing.

At Connect-2 Technology, our technicians are trained to IPC/WHMA-A-620 requirements for cable and wire harness assemblies, supporting consistent workmanship across crimping, termination and assembly processes.

2. Vibration and Mechanical Wear

Wiring inside electrical equipment is rarely installed in isolation. Harnesses may be routed alongside enclosure edges, components, mounting hardware and other cables.

If a harness can move repeatedly against another surface, vibration can gradually damage the outer insulation or protective sleeving.

Routing is therefore an important part of both equipment design and installation.

Harnesses should be supported appropriately, with consideration given to bend radius, fixing points, sharp edges and areas where movement could occur.

Protective sleeving, conduit or other forms of mechanical protection may also be specified where the application requires them.

During maintenance, visible signs of rubbing, chafing or movement can provide an early indication that a wiring harness requires attention.

3. Heat and Temperature Variation

Temperature can have a significant effect on electrical assemblies over their working life.

Switchgear and control equipment may experience heat generated by surrounding components as well as changes in ambient temperature. Materials must therefore be suitable for the conditions in which the finished equipment will operate.

Excessive heat can contribute to deterioration of insulation and other harness materials, while repeated temperature changes can place additional stress on connections and components.

Wire type, insulation, terminals, connectors and sleeving should consequently be specified with the operating environment in mind.

Where a wiring harness forms part of safety equipment or power distribution equipment, understanding those operating conditions before manufacture helps ensure the assembly is built to the correct specification.

4. Moisture and Corrosion

Moisture can also affect wiring harness reliability, particularly in equipment installed outdoors or in humid, industrial or changing environments.

If moisture reaches exposed conductor surfaces or electrical contacts, corrosion can develop over time and affect the integrity of the connection.

The level of protection required will depend on the application and enclosure. Appropriate connectors, seals, cable entry arrangements and materials can all form part of the overall equipment design.

Maintenance teams should also consider the condition of wiring and connections when inspecting equipment for evidence of moisture or corrosion.

HSE guidance on electrical switchgear recommends maintenance appropriate to the equipment and includes examination of wiring, secondary contacts and cable termination areas.

5. Routing and Strain

Even a correctly manufactured wiring harness can be compromised if it is subjected to unnecessary mechanical stress when installed.

Tight bends, tension at connector entry points, trapped wires or insufficient support can place strain on conductors and terminations.

For more complex wiring systems, clearly defined harness layouts can make assembly more repeatable and help ensure branches, breakout points and connections are positioned consistently.

Connect-2 manufactures wiring harnesses to customer drawings and specifications, with harness boards or defined build layouts used where appropriate to support repeatable manufacture.

Providing clear information at the manufacturing stage can also make installation and future replacement considerably easier.

6. Incomplete Specifications and Documentation

Not every wiring harness problem starts with physical damage.

Incomplete drawings, outdated specifications or inconsistent identification can make complex wiring systems harder to manufacture, install and maintain.

A defined manufacturing specification should capture relevant information such as wire types, finished lengths, terminals, connectors, identification, sleeving and harness layout.

Clear wire and connector identification can also make a considerable difference when equipment is being assembled, maintained or fault-found.

Where replacement harnesses are required for existing equipment, drawings, manufacturing information and physical samples can often be used together to establish an accurate build requirement.

Wiring Harness Maintenance and Failure: What Should Engineers Look For?

There is no single maintenance routine that applies to every wiring harness or item of switchgear. Inspection and maintenance should be appropriate to the equipment, its operating environment and the manufacturer's requirements.

However, visible inspection can help identify potential problems such as:

    • damaged or discoloured insulation
    • loose or damaged connectors
    • chafing where wires contact surrounding parts
    • excessive strain or unsupported cable runs
    • corrosion or evidence of moisture
    • damaged identification or unclear wiring routes

The UK Health and Safety Executive's guidance on keeping electrical switchgear safe also emphasises inspection and maintenance of wiring, contacts and termination areas as part of maintaining switchgear.

For manufacturers of switchgear, safety equipment and power distribution systems, reliability starts earlier: with a wiring harness that is manufactured consistently to a clearly defined specification.

Wiring Harness Manufacturing from Connect-2 Technology

Connect-2 Technology has manufactured custom cable assemblies and wiring harnesses in the UK since 1995.

We support manufacturers across sectors including power distribution and safety equipment, producing assemblies from customer drawings, specifications and samples.

Our capabilities include cut and prepared wires, cable assemblies, wiring harnesses, control panels and electronic box builds, with inspection and testing agreed according to the requirements of the project.

If you are looking for a UK manufacturing partner for a new or existing wiring harness requirement, contact our team to discuss your application.

FAQs

Why do wiring harnesses fail in switchgear?

Potential causes include damaged or poor-quality terminations, vibration, abrasion, excessive heat, moisture, unsuitable routing and mechanical strain. The specific cause will depend on the equipment, installation and operating environment.

Why can complex wiring harnesses make maintenance more difficult?

Harnesses with multiple branches, connectors and routing paths can take longer to inspect and fault-find, particularly where identification or documentation is unclear. Consistent wire identification, defined layouts and accurate manufacturing documentation can make maintenance easier.

How can wiring harness failures be reduced?

Good manufacturing controls, appropriate material selection, clear specifications, suitable routing and regular inspection can all help reduce the risk of wiring harness problems during the life of the equipment.

What should be checked when maintaining a wiring harness?

Checks will depend on the equipment and manufacturer's maintenance requirements, but engineers may look for damaged insulation, loose or damaged connections, signs of abrasion, excessive strain, corrosion and evidence of overheating.

Does Connect-2 manufacture wiring harnesses for switchgear and power distribution equipment?

Yes. Connect-2 Technology manufactures custom wiring harnesses, cable assemblies and prepared wires for a range of equipment manufacturers, including applications within the power distribution and safety equipment sectors.