Wiring harness

A wiring harness is a set of wires prepared for one particular job: cut to exact lengths, fitted with plugs, and often bundled together so it can be fitted into a product in one go. A car contains kilometers of harness; a TV has a few short ones.

It is made from insulated wire and connectors. A machine pulls wire from a reel, cuts it to length and strips a little insulation off each end. Small metal terminals are crimped on, squeezed so tightly around the bare copper that the joint is strong and airtight without solder. Each terminal is pushed into its place in a plastic connector housing until it clicks and locks. The wires may then be twisted, taped or tied into a neat bundle, and every finished harness is tested for correct connections. Inserting terminals is fiddly, so much of this work is still done by hand.

In the television, harnesses carry power from the power supply board to the main board and the backlight, and sound to the speakers. Because they plug in rather than being soldered, boards are quick to fit in the factory and easy to swap in repairs.