Finding a reliable custom wire harness supplier for industrial equipment involves more than comparing unit prices. The quality of the RFQ review process, the supplier’s ability to interpret engineering drawings, their sample management workflow, and their production consistency all determine whether the relationship works at scale.
This case study documents how a US-based industrial equipment manufacturer sourced a custom wire harness program with Nexharn Connectivity — from initial inquiry through to repeat production orders. The details have been generalized to protect commercial information, but the sourcing process is representative of how B2B wire harness programs are structured for industrial OEM buyers.
The Buyer: US Industrial Equipment Manufacturer
The buyer manufactures industrial control equipment for North American factory automation applications. Their equipment includes control panels, machine interface units, and power distribution modules — all of which require internal wiring, external cable connections, and sub-assembly harnesses that meet specific pinout, wire gauge, and connector requirements.
The company had previously sourced wire harnesses from a domestic supplier, but rising unit costs and extended lead times prompted their procurement team to evaluate overseas alternatives. The buyer’s requirements included:
- Custom pinout configuration based on internal engineering drawings
- Specific connector models (Molex and JST series) already specified in their BOM
- Wire gauge mix: 20 AWG for power circuits, 24 AWG for signal circuits
- Wire colors following their internal color coding standard
- Continuity and pull-force testing before shipment
- UL-rated wire stock for compliance with North American machine safety standards
The Challenge: Finding a Custom Wire Harness Supplier That Could Match the Drawing
The buyer’s procurement team had contacted several overseas harness suppliers before approaching Nexharn. Two of the three previous contacts had returned quotes without reviewing the drawings in detail — they had simply estimated from the connector count and wire count in the initial email. One supplier had returned a sample that did not match the pinout, requiring a resampling cycle that delayed the qualification timeline by three months.
The core problem was that the buyer’s harness required a specific circuit layout with branch lengths, label positions, and a splice point that is easy to misread from a drawing if the supplier does not have an experienced engineering review step in their RFQ process.
When the buyer contacted Nexharn, they provided the following documentation in their first RFQ email:
- A 2D wiring harness drawing with branch dimensions and tolerances
- A connector BOM with part numbers for all 6 connector positions
- A wire list specifying gauge, color, and circuit function for each conductor
- A test requirement document specifying continuity check and pull force standard
- Target annual quantity: 2,400 units per year in 4 planned releases
The Nexharn RFQ Review Process
Nexharn’s engineering team reviewed the drawing package within two business days and returned a clarification list covering the points that would affect tooling, material sourcing, and sample construction before committing to a quotation.
The clarification points included:
Connector Model Confirmation
Two of the six connector positions specified Molex part numbers that had been superseded by updated series with different housing dimensions. Nexharn confirmed whether the buyer required the exact legacy part (which had longer lead times) or would accept the equivalent current series with an updated drawing revision.
The buyer confirmed that the updated series was acceptable, which reduced the connector sourcing lead time from 8 weeks to 3 weeks for sample production.
Wire Standard Clarification
The drawing specified “UL-rated” wire without a specific UL style number. For 20 AWG and 24 AWG wire in an industrial panel environment, the applicable styles are typically UL 1007, UL 1015, or UL 3266 depending on temperature rating and jacket thickness. Nexharn provided the applicable style options with their respective voltage and temperature ratings and confirmed which matched the buyer’s application environment.
This detail matters because the correct UL style affects the wire OD, which affects the final harness OD and the routing fit through the cable gland and tie-down points on the equipment panel.
Splice Point Construction
The harness drawing included a splice point where two 24 AWG conductors joined a single 20 AWG run. The drawing did not specify the splice construction method. Nexharn offered three options — solder splice with heat shrink, crimp splice with butt connector, or ultrasonic weld splice — and described the trade-offs in terms of cycle life, water resistance, and cost. The buyer selected the crimp splice with adhesive-lined heat shrink for its field service repairability.
Sample Production and Approval
After the clarification exchange was resolved, Nexharn produced five pre-production samples within 14 business days. The sample set was built to the confirmed drawing revision, using the updated Molex series, the selected UL wire styles, and the crimp splice construction.
Each sample was tested for continuity across all circuits before shipment, with the test records included in the sample package. The buyer’s engineering team performed the following checks on receipt:
- Pinout verification against the drawing using a continuity tester
- Branch length measurement at three points per branch
- Connector insertion and extraction force check against the specified standard
- Visual inspection of splice area and heat shrink coverage
- Label position and print quality review
The samples passed all checks with one minor exception: one label was offset by 8mm from the specified position. Nexharn acknowledged the label placement deviation and corrected the assembly jig setting before the production build. The buyer approved the samples without a second sample cycle.
Production Order Structure
The buyer structured the initial production order as a blanket order with four scheduled releases of 600 units each over a 12-month period. This gave Nexharn sufficient volume to amortize the material sourcing and production setup across the year, while giving the buyer the flexibility to adjust quantities on the later releases based on equipment sales performance.
Nexharn managed the connector and wire stock against the blanket order schedule, sending pre-production notification 21 days before each scheduled release to confirm any changes. No specification changes were requested over the four production releases in the first contract year.
Quality Documentation for Each Shipment
Each production shipment included:
- A continuity test record covering 100% of units
- A packing list with unit count, carton dimensions, and gross weight
- A certificate of conformance referencing the drawing revision and applicable UL wire style
- Photographs of the harness assembly and labeling from each production batch
The buyer’s incoming inspection team performed a sampling-based dimensional and continuity check on each delivery, with zero defects recorded across the four production releases in the first year.
What Made This Sourcing Program Work
Looking at the sourcing program from start to finish, several factors contributed to its success — and they are all factors that a buyer can plan for when evaluating a custom wire harness supplier:
Complete Documentation at RFQ Stage
The buyer provided a drawing, BOM, wire list, and test requirement document in their first inquiry. This gave Nexharn enough information to identify the technical questions that would affect sampling — rather than returning a broad quote that would require multiple rounds of follow-up. Buyers who provide complete documentation at RFQ stage consistently experience shorter sample timelines and fewer surprises at production.
Pre-Defined Test Requirements
Having a written test requirement document — specifying which tests would be performed, to what standard, and what the pass/fail criteria were — eliminated ambiguity about what “tested” meant. This is a detail that many industrial buyers overlook when sourcing from overseas for the first time. If the test requirement is not specified in writing, different suppliers will interpret “continuity tested” in different ways.
Blanket Order Structure for the First Year
The blanket order structure gave Nexharn the ability to stock materials and plan production without holding the buyer to a single large up-front commitment. For custom harness programs where the connector models and wire styles are specific to the buyer’s drawing, a blanket order with scheduled releases is almost always a better arrangement than quarterly spot orders, both for lead time management and for material cost stability.
Key Considerations When Selecting a Custom Wire Harness Supplier
Based on this sourcing experience and the common patterns we see across industrial OEM buyer inquiries, the following factors most reliably differentiate capable custom wire harness suppliers from those that will cause problems at scale:
- Drawing review capability: Can the supplier identify specification gaps in your drawing before sampling? A supplier that returns a quote without flagging any questions is often one that will produce to a misinterpreted drawing.
- Material traceability: Can the supplier confirm the origin and certification of the wire stock, connectors, and terminals they are using? For UL-rated programs, this matters for compliance documentation.
- Test records: Does the supplier provide test records per shipment, or only on request? This affects your incoming inspection process and your traceability in case of field returns.
- Production consistency: Does the supplier use assembly jigs and crimp force monitoring, or is assembly done by judgment? Jig-based assembly is the baseline for a production harness that will repeat correctly across batches.
Nexharn’s wire harness manufacturing program covers custom assemblies for industrial, automotive, and commercial applications. If you are starting a custom wire harness sourcing program, we recommend reviewing our RFQ process and preparing a drawing package before your first contact — the more complete the information you provide, the faster and more accurate the initial review will be.
Starting a Custom Wire Harness Program with Nexharn
If your company is evaluating a custom wire harness supplier for an industrial or commercial application, the starting point is a complete RFQ package. At minimum, this should include a harness drawing with branch dimensions and tolerances, a connector BOM with part numbers, a wire list with gauge and color specifications, and any test requirements that will govern acceptance at incoming inspection.
Nexharn reviews each drawing package and returns a clarification list before quoting. This step takes 1–3 business days and prevents misaligned samples. After clarifications are resolved, we structure the sample timeline, production quote, and blanket order format based on the confirmed specification.
Contact Nexharn to start your wire harness RFQ review. Include your drawing, BOM, wire list, and estimated annual quantity to receive an accurate initial response. You can also read our wire harness sourcing checklist for more detail on preparing an RFQ that results in a fast, accurate quotation.