Cable Harness Assembly Guide: Design, Crimping, Testing and Delivery



Cable harness assembly is the controlled manufacturing process of turning wires, terminals, connectors, labels, sleeves, and drawings into a finished electrical interconnect system. For OEM buyers, the most important question is not only “what is a cable harness?” It is “can this supplier build the harness consistently, test it correctly, and document it well enough for production?”

This guide explains the complete cable harness assembly process from RFQ review to delivery. It also shows what information buyers should send before quoting, what happens during wire cutting and crimping, how harness boards are used, which inspections matter, and how to avoid common defects.

If you are sourcing a custom cable harness, the fastest path is to send the drawing, BOM, connector part numbers, wire specifications, quantity, test requirements, and application environment. With those details, soulin can review manufacturability and prepare a more accurate quotation.

Quick Answer: What Is the Cable Harness Assembly Process?

The cable harness assembly process usually includes specification review, material preparation, wire cutting, wire stripping, terminal crimping, terminal insertion, harness board layout, bundling, labeling, electrical testing, visual inspection, and packaging.

A typical OEM cable harness process looks like this:

1. Review the drawing, BOM, connector models, wire gauge, and electrical requirements.
2. Confirm manufacturability, replacement options, tolerances, and test requirements.
3. Cut wires to length and strip insulation according to the drawing.
4. Crimp terminals with controlled tooling and inspect crimp height, pull force, and appearance.
5. Insert terminals into connector housings and confirm locking position.
6. Build the harness on a harness board or fixture to control branch length, routing, and breakout position.
7. Add labels, sleeves, tubes, heat shrink, ties, and protective materials.
8. Perform continuity, short-circuit, polarity, and application-specific electrical tests.
9. Complete final visual inspection, documentation, and packaging.

For OEM programs, the strongest suppliers treat cable harness assembly as a repeatable manufacturing system, not as manual wiring only.

Buyer and RFQ Checklist for Custom Cable Harness Assembly

Before requesting a quote, prepare as much of the following information as possible. Complete RFQ data helps the supplier reduce assumptions, identify risks early, and quote the correct materials and process time.

Scroll horizontally to view the full table.

RFQ Item	What to Send	Why It Matters
Drawing or wiring diagram	PDF, CAD drawing, pinout table, or marked sample	Defines wire routing, pin assignment, length, branches, labels, and tolerances
BOM	Connector, terminal, wire, sleeve, tube, label, tie, and accessory part numbers	Controls material selection, sourcing time, and substitution review
Connector details	Brand, series, part number, male/female, pitch, lock type, waterproof rating	Prevents mating mismatch and terminal compatibility problems
Wire specification	AWG or mm2, insulation material, color, rating, shielding, jacket	Affects current capacity, flexibility, stripping, crimping, and environment fit
Quantity	Prototype quantity, pilot run, annual volume, delivery schedule	Determines tooling approach, unit cost, and production planning
Application environment	Automotive, industrial, medical, consumer, outdoor, vibration, heat, oil, moisture	Guides connector, jacket, sleeve, strain relief, and testing choices
Test requirements	Continuity, hi-pot, insulation resistance, pull-force, custom fixture test	Defines quality control steps and test fixture needs
Samples or photos	Existing harness sample, connector photos, installed-space photos	Helps confirm routing, breakout direction, clearance, and assembly constraints
Packaging requirements	Bags, labels, lot traceability, kitting, cartons, ESD handling	Protects parts during shipping and supports receiving inspection
Compliance needs	RoHS, REACH, UL-recognized materials, customer-specific requirements	Ensures material and documentation alignment before production

If you do not have a complete drawing yet, send a sample, photos, connector information, and the function of each wire. soulin can help review the structure and suggest the missing details needed for quotation.

Wire Harness Assembly Process Table

The table below summarizes the main production steps for OEM cable harness manufacturing.

Scroll horizontally to view the full table.

Process Step	What Happens	Key Control Points	Typical Output
1. RFQ and specification review	Supplier checks drawing, BOM, pinout, test needs, and application environment	Missing dimensions, terminal compatibility, wire gauge, substitutions, tolerances	Quote basis and engineering questions
2. DFM and sample confirmation	Manufacturing team reviews whether the harness can be built efficiently and tested reliably	Bend radius, branch length, connector orientation, label position, fixture feasibility	Confirmed build method or DFM feedback
3. Material preparation	Connectors, terminals, wires, sleeves, labels, tubes, and accessories are prepared	Approved parts, correct colors, correct wire size, incoming inspection	Ready materials for production
4. Wire cutting	Wires are cut to specified length using manual or automated equipment	Cut length tolerance, wire color, batch separation, quantity count	Cut wire sets
5. Wire stripping	Insulation is stripped from wire ends to expose conductor for crimping or soldering	Strip length, no nicked strands, no damaged insulation	Prepared wire ends
6. Terminal crimping	Terminals are attached to stripped wire using controlled crimp tooling	Crimp height, conductor brush, insulation support, pull-force, tooling condition	Crimped wire leads
7. Terminal insertion	Crimped terminals are inserted into connector housings according to pinout	Correct cavity, terminal lock, insertion direction, tug test	Populated connectors
8. Harness board assembly	Wires are routed on a fixture or board to control branch shape and length	Branch length, breakout point, connector orientation, bend radius	Harness shape matches drawing
9. Bundling and protection	Tape, braided sleeve, corrugated tube, heat shrink, tie wraps, or jackets are applied	Coverage, strain relief, abrasion protection, flexibility	Protected harness assembly
10. Labeling and documentation	Labels, part numbers, serials, date codes, and inspection records are added	Label content, position, durability, traceability	Identifiable and traceable harness
11. Electrical testing	Harness is tested for continuity, shorts, polarity, and custom requirements	Test fixture setup, pin-to-pin map, pass/fail record	Verified electrical function
12. Final inspection and packaging	Visual checks, dimensional checks, cleaning, bagging, and cartons are completed	Defects, missing accessories, connector damage, packing protection	Ready-to-ship cable harnesses

This process may be adjusted for simple jumper cables, complex automotive harnesses, medical device cables, industrial control harnesses, waterproof cable assemblies, or mixed connector assemblies.

Materials and Connector Selection

Material selection has a direct effect on electrical performance, durability, cost, and lead time. For custom cable harness assembly, the main materials include wires, terminals, connector housings, seals, sleeves, jackets, labels, heat shrink, tapes, and protective tubes.

Wire selection

Choose wire based on current, voltage, flexibility, temperature, space, and application environment. Common buyer inputs include:

• AWG or cross-section size
• Conductor material and strand count
• Insulation material
• Wire color
• Rated voltage and temperature
• Shielded or unshielded structure
• Single wire, ribbon cable, multi-core cable, coaxial cable, or twisted pair

For applications with repeated movement, vibration, or tight routing, flexibility and bend radius matter as much as electrical rating.

Connector and terminal selection

Connector selection should start from the mating interface and environment:

• Board-to-wire connectors for PCB connection
• Wire-to-wire connectors for internal harness routing
• Circular connectors for industrial equipment
• Waterproof connectors for outdoor or harsh environments
• FFC/FPC connectors for compact electronics
• RJ45, M12, USB, D-sub, or other interface connectors where required by the device

The terminal must match the connector housing and wire size range. A connector part number alone is not always enough. The terminal series, plating, wire range, seal compatibility, and crimp tooling should also be checked.

Protective materials

Protective materials are selected according to abrasion, heat, chemical exposure, installation space, and appearance requirements:

• PVC tube for simple bundling
• Corrugated tube for mechanical protection
• Braided sleeve for abrasion resistance and flexibility
• Heat shrink tube for insulation, strain relief, and branch protection
• Adhesive-lined heat shrink for moisture resistance
• Tape wrapping for routing and noise reduction
• Labels for part identification and installation guidance

When the harness will be installed near motors, engines, metal edges, or moving parts, protection should be reviewed early instead of added after sample failure.

Crimping and Terminal Insertion

Crimping is one of the most important steps in cable harness assembly. A good crimp creates a stable mechanical and electrical connection between the conductor and terminal without cutting strands, leaving loose wires, or damaging insulation.

What a good crimp should control

A controlled crimp process checks:

• Correct terminal and wire size
• Correct strip length
• Proper conductor placement
• Proper insulation support
• No missing or cut strands
• No over-crimping or under-crimping
• Correct crimp height where specified
• Pull-force result where required
• Clean terminal shape without deformation that blocks insertion

For production projects, crimping should be done with the correct applicator or tooling, and the first pieces should be inspected before the batch continues.

Terminal insertion into connector housings

After crimping, terminals are inserted into connector housings according to the pinout. This step must prevent wrong-cavity insertion, incomplete locking, bent terminals, and reversed connector orientation.

Common checks include:

• Pin number verification against drawing
• Visual confirmation of terminal orientation
• Audible or tactile lock confirmation where applicable
• Light tug test after insertion
• Secondary lock or TPA installation where the connector uses one
• Final pin-to-pin continuity test

Many harness failures come from terminals that look inserted but are not fully locked. This is why terminal insertion must be verified before final bundling hides the wires.

Harness Board Assembly and Routing Control

A harness board, also called a nail board or assembly fixture, helps control the physical shape of the wire harness. It guides operators on wire routing, branch position, connector direction, overall length, and accessory placement.

Harness boards are especially useful when the assembly includes:

• Multiple branches
• Several connector types
• Fixed breakout points
• Tight installation spaces
• Repeated production quantities
• Labels, clips, sleeves, or protective tubes at defined positions

During harness board assembly, wires are routed along the fixture, grouped into branches, and secured with tape, ties, sleeves, or tubing. The board helps keep the finished harness consistent from one unit to the next.

For OEM buyers, a harness board is also a sign that the supplier has translated the drawing into a repeatable build method. This matters when moving from prototype to mass production.

Labeling, Documentation and Traceability

Labels and documentation make the finished cable harness easier to install, inspect, replace, and trace. For OEM production, this is more than cosmetic. It reduces installation mistakes and helps quality teams identify batch information.

Common labeling and documentation items include:

• Part number label
• Revision label
• Wire number label
• Connector position label
• Date code
• Lot number
• Serial number where required
• Pass/fail test record
• Inspection report
• Packing label

Label material should match the environment. A label used inside a dry device enclosure may not need the same durability as a label exposed to oil, heat, water, or outdoor conditions.

Documentation requirements should be discussed during the RFQ stage. If the buyer needs a test report, material declaration, photo record, or first article inspection, the supplier should know this before production begins.

Testing and Quality Control for Cable Harness Assembly

Testing confirms that the cable harness matches the electrical design before shipment. The exact test plan depends on the product, application, and buyer requirements.

Common electrical tests

Scroll horizontally to view the full table.

Test Type	What It Checks	Why It Matters
Continuity test	Confirms each wire connects to the correct pin	Prevents open circuits and wrong wiring
Short-circuit test	Checks that unintended connections are not present	Prevents device damage and safety risks
Polarity test	Confirms positive, negative, signal, and ground lines are in the correct positions	Prevents reverse wiring and functional failure
Hi-pot test	Applies high voltage where required to check insulation withstand	Used for higher-voltage or safety-critical assemblies
Insulation resistance test	Checks resistance between isolated circuits	Helps identify insulation weakness or contamination
Pull-force test	Measures crimp retention force	Confirms terminal crimp strength
Visual inspection	Checks physical defects, labels, damage, and completeness	Catches issues that electrical tests may miss

Visual and process inspections

Quality control should also include physical inspection:

• Correct wire color and gauge
• Correct connector orientation
• Correct terminal insertion
• No exposed conductor outside the terminal area
• No damaged insulation
• No bent pins
• No missing seals, locks, sleeves, labels, or accessories
• Correct branch length and harness shape
• Clean packaging without crushing connectors

For complex harnesses, a dedicated test fixture can reduce manual checking errors and provide a clearer pass/fail record.

Common Cable Harness Defects and How to Prevent Them

Scroll horizontally to view the full table.

Defect	Likely Cause	Prevention Method
Open circuit	Broken conductor, missed crimp, terminal not fully seated	Continuity test, tug test, controlled terminal insertion
Short circuit	Wrong wiring, damaged insulation, exposed strands	Pinout verification, strip-length control, visual inspection
Wrong pinout	Terminal inserted into wrong cavity	Color-coded work instructions, pin map, electrical test fixture
Weak crimp	Wrong tooling, incorrect crimp height, wrong wire size	Tooling setup, first-piece inspection, pull-force testing
Over-crimped terminal	Excessive compression or wrong applicator	Crimp height control and tooling maintenance
Damaged insulation	Incorrect stripping blade, handling damage, sharp routing edge	Strip machine setup, operator training, routing protection
Loose terminal	Incomplete lock, wrong terminal, missing secondary lock	Terminal compatibility check, tug test, lock verification
Connector mismatch	Incorrect connector series or gender	BOM review, mating sample check, incoming inspection
Label missing or unreadable	Label process not defined, wrong label material	Label checklist, durable material selection, final inspection
Harness too short or branch off-position	Drawing tolerance unclear, no harness board	Fixture build, length inspection, drawing clarification
Poor strain relief	Sleeve, tie, or boot missing near stress point	DFM review and protective accessory placement
Packaging damage	Connectors not protected during shipping	Individual bagging, caps, trays, carton support

Preventing these defects starts before production. A complete drawing, clear pinout, approved materials, and defined inspection plan will reduce rework and delivery risk.

How to Request a Quote for Custom Cable Harness Assembly

To request a reliable quote, send soulin the information that defines the harness electrically, mechanically, and commercially.

Minimum information for quotation

Please send:

• Drawing, wiring diagram, or sample photo
• Connector part numbers or connector photos
• Wire gauge, color, length, and insulation requirement
• Pinout or circuit map
• Quantity for prototype and production
• Application environment
• Required tests
• Required labels, packaging, or traceability
• Target lead time

Better information for faster quoting

For a faster and more accurate quotation, also include:

• BOM with approved manufacturers
• 2D or 3D drawing
• Existing sample harness
• Mating connector or device information
• Installation-space photos
• Compliance requirements
• Annual usage estimate
• Delivery schedule by batch

What soulin can help review

soulin can support custom cable harness projects by reviewing:

• Connector and terminal compatibility
• Wire gauge and material selection
• Harness routing and branch layout
• Crimping and terminal insertion process
• Labeling and documentation requirements
• Continuity and custom test requirements
• Prototype-to-production manufacturability

Send your drawing, BOM, or sample information to request an OEM cable harness assembly quote.

FAQ