How to Prepare a Wire Harness RFQ for Vietnam Manufacturing

A schematic communicates electrical intent. A physical harness drawing communicates how that intent becomes an assembly: connector locations, overall and branch lengths, breakout locations, routing, labels, sleeving, heat shrink, splices, clips or mounting features, and important dimensions or tolerances.

Dimensions should identify clear reference points, such as a connector face, strain-relief point, breakout, or branch end. Tight tolerances should be used only where the application needs them.

Every conductor needs an unambiguous from-to definition. A wire list, spreadsheet, or pinout table often provides the clearest starting point. The format below is illustrative rather than mandatory.

More complex harnesses may also identify signal names, wire part numbers, shields, twisted pairs, and splices.

A bill of materials identifies the physical components intended for the assembly. A harness BOM may include wire, connector housings, contacts or terminals, seals, backshells, heat shrink, sleeving, labels, clips, and other specified hardware.

Useful fields can include manufacturer, manufacturer part number, description, quantity, customer part number, and a revision or specification reference where applicable. The drawing shows how the harness is physically assembled; the BOM identifies the specified materials and components used to build it.

If an exact manufacturer part number is mandatory, make that clear. If equivalent components may be proposed, define whether customer approval is required before substitution. A harness does not need to use one particular BOM format as long as the intended materials are unambiguous.

Specifying only a connector housing may not be sufficient. A connector family can use different contacts or terminals depending on wire size, plating, material, and application requirements.

Useful details include manufacturer, connector family, housing part number, contact or terminal part number, mating connector, number of positions, wire size, datasheet, and photographs. When the exact part is not yet known, the available interface and application information can still help identify what needs to be selected.

Useful wire information includes AWG or conductor size, color, insulation, temperature rating, voltage rating, stranding, shielding, and any relevant wire specification. When an exact wire has not been selected, the application requirements can help frame the remaining selection work.

Current, temperature, flexibility, abrasion, oil, moisture, and repeated movement are examples of conditions that may matter. Those conditions should be stated as project requirements, rather than assumed from a general description.

A pinout identifies the electrical function at each cavity. A connector may look different depending on whether it is viewed from the mating face or the wire-entry side. Always identify the view shown, and use the connector manufacturer's drawing as the authoritative reference for cavity numbering and orientation.

Specify overall length, branch lengths, breakout locations, and the reference points used to measure them. The harness drawing above illustrates how a main trunk and separate branches can be dimensioned without overloading a schematic.

Appropriate tolerances help a manufacturer understand where fit is critical and where practical assembly variation is acceptable.

Protection may include braided sleeving, corrugated loom, heat shrink, protective tape, conduit, grommets, or strain relief. The operating environment matters: heat, vibration, moisture, chemicals, sharp edges, and movement can all affect the required construction.

State any required J1/J2 connector labels, individual wire identification, heat-shrink labels, assembly part number, revision, or serial number. Prototype identification may be simpler than repeat-production traceability, so it helps to distinguish what is needed for the present build from what is expected later.

Common checks may include continuity, absence of unintended shorts, pin-to-pin verification, and visual inspection. Depending on the project, additional specified requirements might include crimp inspection, pull-force testing, crimp-height measurements, insulation-resistance testing, dielectric-withstand testing, or customer-specific functional testing.

Not every harness requires every test. Testing and acceptance requirements should be defined for the particular assembly.

Quantity affects setup, sourcing, tooling, fixture preparation, and unit cost. A useful request may state: prototype quantity: 2; initial production quantity: 25; expected annual quantity: approximately 200. These are planning inputs, not a pricing commitment.

Basic revision control keeps a quote, approved build package, and order aligned. For example, an illustrative assembly might be identified as BH-1024, Revision B. The quoted, approved, and ordered documentation should all refer to the correct revision.

State whether substitutions are allowed and what approval is required. A simple instruction such as No substitutions without customer approval. removes a common source of uncertainty. Components should not be substituted independently without an agreed process.

If a project requires a particular workmanship or acceptance standard, state it clearly. IPC/WHMA-A-620 is one example of a cable-and-wire-harness assembly standard a customer may reference. A requirement should be identified as part of the project scope; it should not be assumed from a general inquiry.