A harness fails more often at its protection than at its wire. Rubbing, heat, fluid and vibration attack the harness where it passes through panels, brackets and moving joints. The chart below matches the common protective materials to the hazard they address. It is a selection aid, not a replacement for the customer drawing or the vehicle manufacturer’s specification.
Protection materials by purpose
| Material | Typical use | Main hazard addressed | What to check |
|---|---|---|---|
| Corrugated conduit (split or closed) | Bundles of wires along a run | Abrasion and routine handling | Check the material grade for the temperature and fluid exposure of the location. |
| Braided sleeve | Flexible sections and breakouts | Abrasion and bundling, some heat tolerance depending on material | Check the temperature rating of the sleeve material. |
| Harness tape | Binding and light wrapping | Binding, rattle and light abrasion | Tape type must suit the temperature zone and the wire insulation. |
| Heat shrink sleeve | Terminations and splices | Sealing and strain relief at joints | Check shrink ratio and whether it carries adhesive for sealing. |
| Grommet | Where the harness passes through a panel | Edge cutting and water ingress | Confirm hole size and seating. |
| Cable clip or saddle | Fixing to body or frame | Movement and chafing | Clip pitch and orientation come from the drawing. |
| Overmould | Connector backshell or breakout | Sealing and strain relief in a single part | Specified on the drawing, usually for complex assemblies. |
Using the chart
Start with the hazard map of the route: heat, fluid, vibration, abrasion and water. Then pick the protection that matches the worst hazard in each section, not the average. A single harness can need four different protective materials along its length.
The insulation under the protection also matters. APAR automotive wire includes e-beam cross-linked GXL, TXL and SXL types to ISO 6722 Types C and D, as listed on the automotive and EV harness page. For wire options, see the automotive wires and cables range. For routing and fixing practice in rail, see the rolling stock harness routing guide.