How to Spec a Wire Harness for Manufacturing
A practical checklist for engineers writing a wire harness spec — connectors, wire gauge, environmentals, testing, and documentation.
A great wire harness spec answers five questions before it hits the shop floor: what connects to what, in what environment, at what current, to what workmanship standard, and with what documentation.
Start with a schematic and a physical layout drawing. Call out every connector, pin, and wire by part number. Specify wire gauge and jacket rating for the current and temperature the harness will see. Note bend radius, service loops, and strain relief locations.
For the environment, name it: indoor cabinet, outdoor solar array, avionics bay, EV battery pack. Each of those implies a different jacket, seal, and connector family. Don't leave it to interpretation.
Pick a workmanship standard. IPC/WHMA-A-620 Class 2 is a sane default; Class 3 for aerospace, medical, and high-reliability. Specify the test regime: continuity, hipot voltage and duration, insulation resistance, pull test, VSWR if RF.
Finally, list your documentation asks: Certificate of Conformance, material traceability, first-article inspection, photo documentation. A one-page spec with these five sections gets you an accurate quote and a build that matches your intent.
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