Best practices for handling, routing and installation.

A few simple guidelines to follow during cable harness handling, routing and installation will extend their life, ensure peak performance, facilitate installation and repairs, and provide a visible sign of quality workmanship.

Damage to wires shortens the connection life and could impact the function of associated circuits. Dressing the wires and cables entering and exiting the bundle presents a neat appearance and facilitates future work on the cable. Strain relief on all terminated ends of a cable or harness will make it easier to install and facilitate an easier repair, if needed. Proper harness routing and shielding will ensure all signals reach their destination free of interference and crosstalk.

Damaged cable (like birdcaging, Figure 1) can be prevented by twisting the insulation from the end of the wire in the same direction and rate as the manufacturer’s twist. This will make soldering into a cup or on a terminal much easier and will prevent shorts. Wires cannot exceed the minimum bend radius as outlined by the manufacturer in IPC-A-610, Acceptability of Electronic Assemblies. Cut or nicked conductors may degrade signal performance of higher frequency applications, as well as compromise the mechanical strength. To prevent nicking or cutting conductors, use a thermal insulation stripper, or correctly sized mechanical strippers, and appropriate hand tools.


Dressing the cable is the process in which all the insulated wires in a wire bundle or harness are arranged so that there are no crossed, folded, strained or loose conductors. Crossed conductors, when tied into a bundle or harness, can lead to crushed insulation in coax cables or split insulation on stranded wire. Many times the crossed conductors are easily loosened and can be pulled and broken.

When breaking a wire or conductor out of a harness or bundle, a minimum bend radius of the conductor and required strain relief must be observed (Figure 2). The location of the termination and the breakout point should permit the wire to curve gradually to the termination. This prevents overbending and provides enough wire for strain relief.


Strain relief is not only important when breaking out of a harness, but is essential at all terminations: post, terminal, screw or multi-pin connectors. If a radio is mobile, or an electrical cabinet can be moved, the strain relief on the conductors and connectors will permit flexing  without breakage.

Temperature extremes can also stress connections, as the wires contract in the cold and expand in the heat. Strain relief, in most cases, can be accomplished by either excess wire between a fixed mounting point and the connector, or a mechanical grip in the conductor. When terminating a wiring harness, strain relief is achieved by adding a maintenance loop before the termination point. A commercially available gripping grommet relief can be used if the conductor is going through a bulkhead or electrical cabinet.

Routing cable assemblies and wiring harnesses can accomplish three goals: neat appearance, signal isolation and integrity, and material savings. When designing the wiring harness routing, low voltage or low data rate busses should not be run next to RF or high voltage AC cables unless the cables have been properly shielded. Even shielded data cables can pick up AC and RF interference when run in the same bundle for long runs.

Also, a well-considered route for cables and conductors can minimize cable lengths and increase material savings when multiplied by the number of products manufactured. Quality workmanship is key to a long service life for harnesses and cables, as well as the associated electronics. IPC-A-610 and IPC-A-620 are industry standards for cable, harness and connector assembly workmanship.

The American Competitiveness Institute (aciusa.org) is a scientific research corporation dedicated to the advancement of electronics manufacturing processes and materials for the Department of Defense and industry. This column appears monthly.

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