The wire harness manufacturing process starts long before a wire is cut. For a custom assembly, the drawing, wire specifications, connector components and inspection requirements must agree. Once these details are confirmed, production moves through wire preparation, termination, assembly, testing and packing.
At Shengxin, we build wire harnesses to customer drawings and reference samples. Here is how a build-to-drawing wire harness moves from an OEM requirement to a finished assembly.
Wire Harness Manufacturing Process at a Glance
The wire harness production process below shows the main steps for custom, build-to-drawing assemblies.
| Step | Manufacturing stage | What gets confirmed |
|---|---|---|
| 1 | Drawing or sample review | Wire specifications, connector views, pinout and dimensions |
| 2 | Material confirmation | Wire, contacts, housings, availability and compatibility |
| 3 | Process planning | Tooling, production method and inspection points |
| 4 | Cutting and stripping | Cut lengths, strip lengths and conductor condition |
| 5 | Termination (crimping or specified end preparation) | Correct termination and workmanship |
| 6 | Housing and harness assembly | Cavity positions, branches, routing and protection |
| 7 | Product-specific finishing | Sleeving, heat shrink, soldering or other specified operations |
| 8 | Inspection and electrical testing | Continuity, pinout and applicable additional checks |
| 9 | Packing and delivery | Identification, quantity, protection and agreed documents |
1. Review the Drawing or Physical Sample
A manufacturing drawing defines what the finished harness must contain: wire style and gauge, colors, connector housings, terminal part numbers, pin assignments, lengths, branch dimensions and relevant tolerances. Clear connector views are especially important. Pin numbering seen from the mating face may appear reversed when viewed from the wire-entry side.
We can also review a physical sample when a complete production drawing is unavailable. The sample helps identify wire and connector details and develop manufacturing documentation for customer review. A proposed drawing and sample assembly are then checked and approved before production.
Confirm these five items before releasing the build:
- Connector housing and contact part numbers
- Wire style, AWG, color and required lengths
- Pinout and the viewing direction used in the drawing
- Branch dimensions, finishing and protection requirements
- Sample approval, inspection requirements and order quantity
Missing details can be resolved during review. An unapproved substitution should never be made solely because two connectors look alike.
2. Confirm Wires, Terminals and Connector Housings
Wire size alone does not establish compatibility. Two wires may share the same AWG but have different insulation diameters. This affects terminal insulation support, tooling selection and the fit of the finished wires in a connector assembly.
The specified housing must also match the correct terminal series and mating component. Matching connector pitch is not enough to prove that two parts are interchangeable.
Material availability affects production planning. Standard components may be readily available, while customer-specified connectors from limited supply channels may require advance procurement. We confirm the lead time for each specified part number against the order before setting the manufacturing schedule.
If a different wire, terminal or connector is proposed, the change is reviewed for compatibility and submitted for customer approval where required.
3. Plan the Manufacturing Method
Production method follows connector type, order quantity, repeatability and assembly complexity. Straightforward, high-repeatability operations may use automated equipment. Short runs and assemblies with multiple branches or unusual terminations can require additional manual operations. Many projects use a combination of methods.
Process planning also identifies the appropriate tooling, first-piece checks, in-process controls and final inspection points. The objective is consistent dimensions, secure terminations and correct electrical connections throughout the order.
4. Cut, Strip and Prepare the Wires
Wires are cut to the specified lengths and stripped for their required terminations. In a branched harness, several wires may have different cut lengths even when they terminate at the same connector.
Cutting and stripping must avoid conductor nicks, cut strands and damaged insulation. The drawing should distinguish finished assembly dimensions from wire preparation dimensions so that the assembled harness fits the customer's equipment.
End preparation follows the design. A stripped and solder-dipped wire end is a different termination from a crimped contact. Wire ends are not automatically tinned before crimping.
5. Crimp the Specified Terminals
A crimp joins the conductor to a terminal (also called a contact) through controlled mechanical deformation. Open-barrel terminals typically have distinct conductor-crimp and insulation-support areas, each with its own function.
The correct tooling and setup depend on the terminal, conductor size, strand construction and insulation diameter. Inspection can include conductor position, crimp formation, visible damage and specified dimensions. Mechanical checks such as pull-force testing are applied according to the relevant process and inspection requirements.
Electrical continuity alone cannot establish crimp strength. A terminal may conduct electricity but still have unacceptable mechanical workmanship.
See how we approach wire harness manufacturing capabilities.
6. Assemble the Connector Housings and Branches
Crimped terminals are inserted into the specified housing cavities according to the approved pinout. Correct cavity assignment, terminal engagement and connector orientation are essential to the finished assembly.
For multi-branch harnesses, assembly also establishes wire routing, branch lengths and the positions of sleeves, ties and other protection. A harness can pass an electrical test yet still fail to fit its intended equipment if the branch geometry is wrong.
7. Apply the Required Finishing Operations
Finishing depends on the drawing. It may include soldered connections, heat-shrink tubing, protective sleeving, bundling, adhesive treatment or labeling. None of these operations is automatically required on every wire harness.
Inspection should occur before a later operation hides a connection that may need verification or rework. For example, a joint that will be covered by sleeving or encapsulation should be checked at the appropriate earlier stage.
Environmental protection, strain relief and special performance requirements must be specified in the product definition.
8. Inspect, Test and Verify Quality
Quality checks start before final testing. Material checks, first-piece confirmation and in-process inspection help identify problems at different stages of production.
For applicable finished connector harnesses, continuity and pinout testing verify that the specified circuits are connected correctly. Shengxin checks continuity and pinout on applicable finished harnesses; visual, dimensional and mechanical inspections follow the product requirements.
Visual and dimensional inspections, connector checks and mechanical tests follow the applicable product requirements. Some mechanical tests are performed on samples because they may damage the tested parts.
100% continuity and pinout testing does not mean every mechanical or environmental property is tested on every piece. Test methods, acceptance criteria and any required inspection documentation are confirmed with the order.
Learn more about our quality controls and wire harness manufacturing capabilities.
9. Pack and Deliver the Finished Harnesses
After inspection, completed assemblies are organized and packed according to the agreed requirements. Identification, quantities and relevant drawing revisions are checked before delivery. Packaging protects the wires, terminals and connector housings during handling and transport.
A change to an approved component, critical dimension or pinout requires review before the revised assembly enters production.
What Should You Send for a Custom Wire Harness Quote?
A complete drawing is useful, but a clear reference sample can also start the discussion. Include the information you already have:
- Drawing, BOM or reference-sample photos
- Wire style, gauge, colors and lengths
- Connector and terminal part numbers, if known
- Pinout, mating-face view and branch layout
- Required finishing, testing and documentation
- Estimated order quantity and delivery target
Our custom wire harness project guide explains how to prepare an inquiry. You can also send your drawings or sample details for a quotation.
Frequently Asked Questions
Can you manufacture a wire harness from a physical sample?
Yes. A reference sample can help establish the manufacturing details, including visible components, routing and dimensions. The proposed documentation and sample assembly are reviewed with the customer before production. Electrical and performance requirements still need to be specified.
Are wire ends always tinned before crimping?
No. Solder-dipped wire ends and crimped terminal connections are different termination types. The drawing and relevant component specifications determine the correct preparation.
Does every wire harness use automated crimping?
No. Equipment and tooling are selected for the terminal type, order quantity and repeatability. Some assemblies require manual operations alongside automated wire preparation or crimping.
Does a continuity test confirm the quality of the entire harness?
Continuity and pinout testing confirm defined electrical connections. Crimp strength, dimensions, workmanship and other product requirements may need separate inspection or testing.
