wiring harness
A bundle of insulated wires, often held together with straps or other connectors, that transmit signals or electrical current within a vehicle, electronic device, etc., or between them.
wiring harness: pre-assembled wire bundles that save assembly time
A wiring harness is a set of wires bundled and routed together, typically held with tape, plastic ties, or adhesive-backed wrapping, designed to connect multiple electrical components in a machine or vehicle. Instead of running individual wires point-to-point, manufacturers assemble harnesses off the production line, then install them as single units. This cuts assembly time and reduces errors in wire routing and connector placement.
Harnesses vary widely by application. An automotive under-dash harness might contain 20 to 50 individual wires ranging from 0.5 mm to 4 mm in diameter, color-coded and terminated with spade connectors, ring terminals, or multi-pin connectors at each end. Industrial control harnesses may use twisted shielded pairs for noise immunity, bundled with heavier gauge conductors for higher current loads. The insulation material (PVC, cross-linked polyethylene, silicone) is chosen for temperature rating, abrasion resistance, and chemical compatibility in the installation environment.
Custom harnesses are built using harness boards, fixtures that hold wire ends in precise positions while technicians strip, tin, and crimp or solder connections. The wires are then dressed along the intended path, secured with cable ties or heat-shrink tubing at intervals, and the bundle is pressure-tested or continuity-checked before shipping. Standard harnesses for high-volume products use semi-automated crimping and bundling equipment to hold cost down.
Harnesses fail when insulation is pinched against sharp edges during installation, when vibration causes fatigue at connector entry points, or when moisture seeps into connectors and causes corrosion. Poor crimp quality on terminals leads to high resistance and heat generation. In harsh environments, UV exposure degrades outer jackets over years of service. Incorrect routing can create shorts if the harness is forced into tight spaces or repeatedly flexed beyond its design radius.
Harness design trades off material cost, assembly labor, and serviceability. A single integrated harness reduces assembly time but makes field repair harder; modular designs with multiple connectors along the run cost more to build but allow technicians to replace sections without rewiring the entire system. The term harness itself comes from the practice of using straps and wrapping, evoking the physical bundling of reins on horse tack.