Procurement Guide

Wire Harness RFQ Checklist:15 Details Manufacturers Need

30% of wire harness RFQs are returned for missing information, causing 2-4 week delays. This checklist ensures your quote request is complete the first time.

The Real Cost: Incomplete RFQs don't just delay quotes—they lead to price variations of up to 40%. You either overpay, or the supplier underestimates and cuts corners.

12 min read
WellPCB Engineering Team

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Why Your RFQ Matters More Than You Think

Here's a frustrating reality: 30% of wire harness Request for Quotes (RFQs) are returned to buyers for missing information. Each round-trip adds 1-2 weeks to your project timeline. Worse, incomplete RFQs lead to quote variations of 30-40%—meaning you're either overpaying or getting a lowball estimate that forces the supplier to cut corners.

The Hidden Complexity

According to industry analysis, a typical wire harness BOM contains 50-100 different items. Each missing specification creates uncertainty that suppliers must account for in their pricing—usually by adding a risk premium. (Source: Cadonix RFQ Challenges Analysis )

Wire harness assembly line manufacturing with quality control inspection for RFQ quotation accuracy

Clear RFQ specifications enable accurate manufacturing quotes and faster project timelines

This guide covers the 15 critical details that wire harness manufacturers need to provide accurate quotes. Use it as your pre-submission checklist, and you'll get better quotes, faster responses, and fewer surprises during production.

Whether you're sourcing custom cable assemblies, automotive harnesses, or industrial wire harnesses, these 15 items apply universally.

1

Part 1: Technical Specifications

Technical specifications form the foundation of any accurate quote. Missing or unclear specs force manufacturers to make assumptions—and assumptions add cost.

1

Assembly Drawing / Wire Harness Drawing

The foundation of any accurate quote. Your drawing should include overall dimensions, branch lengths, connector positions, and breakout points.

Must Include:

  • Title block with part number, revision, and date
  • 2D layout with dimensions (±0.5" tolerance typical)
  • Connector view orientation and pinout
  • Multiple views for complex routing (isometric, side, top)
Common Mistake: Providing only a schematic diagram instead of a manufacturing drawing. Schematics show electrical connections; manufacturing drawings show physical layout.
Pro Tip: Include 3D CAD files (STEP, IGES) when available—they reduce quoting time by 40% and minimize interpretation errors.
2

Bill of Materials (BOM)

A complete parts list with manufacturer part numbers. This is your procurement guide and cost calculation foundation.

Must Include:

  • Manufacturer part numbers for all components
  • Approved alternative/equivalent part numbers
  • Quantity per assembly
  • Wire specifications (AWG, material, insulation type)
Common Mistake: Listing generic descriptions like "4-pin connector" without specifying brand and model. This leads to quote variations of 30-50%.
Pro Tip: Specify whether equivalents are acceptable. Allowing approved alternatives can reduce costs by 15-25% without sacrificing quality.
3

Electrical Specifications

Define the electrical requirements that your harness must meet to ensure proper wire sizing and component selection.

Must Include:

  • Voltage levels (12V, 24V, 48V, high-voltage)
  • Current requirements per circuit (continuous and peak)
  • Impedance requirements (if applicable)
  • Signal types (power, data, analog, digital)
Common Mistake: Undersizing wires based on average current without considering peak loads. This causes overheating and premature failure.
Pro Tip: Always specify with a 20% safety margin. A wire rated for 10A should only carry 8A continuous in bundled applications.
4

Connector and Terminal Details

Connectors often represent 40-60% of harness cost. Clear specifications prevent misquotes and compatibility issues.

Must Include:

  • Connector brand and part number (Molex, TE, JST, Amphenol)
  • Terminal type and size
  • Pinout diagram with wire assignments
  • Mating connector information
Common Mistake: Choosing uncertified low-cost connectors to save money. This often leads to field failures costing 10-50x the initial savings.
Pro Tip: Consider total cost of ownership. A $0.50 connector that fails costs far more than a $2.00 certified connector that lasts.
5

Wire Specifications

Wire selection affects performance, durability, and cost. Be specific about materials and ratings.

Must Include:

  • Wire gauge (AWG or metric)
  • Conductor material (bare copper, tinned copper, copper alloy)
  • Insulation material (PVC, TPE, PUR, silicone, PTFE)
  • Color coding requirements
  • Stranding class (for flex applications)
Common Mistake: Using copper alloy instead of OEM-grade copper for cost savings. Alloy conductors have higher resistance and fail sooner under thermal stress.
Pro Tip: For high-flex applications (robotics, moving equipment), specify Class 6 stranding (665+ strands per conductor) for 10M+ flex cycle life.
6

Tolerance Requirements

Wire harness tolerances differ significantly from machined parts. Set realistic expectations.

Must Include:

  • Length tolerances (typically ±0.5" or ±12mm)
  • Critical dimension callouts
  • Connector position tolerances
  • Any tight-tolerance requirements with justification
Common Mistake: Specifying machining-level tolerances (thousandths of an inch) for wire harnesses. This is unrealistic and drives up costs unnecessarily.
Pro Tip: Standard harness tolerance is ±0.5" (±12mm). Tighter tolerances require special fixtures and increase costs by 20-40%.

For more details on wire specifications, see our Wire Harness Design Guide which covers the American Wire Gauge (AWG) system in detail.

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2

Part 2: Application Environment

Environmental conditions directly affect material selection. A harness designed for an office environment will fail quickly in a factory with oil mist and 50°C ambient temperatures.

7

Operating Environment

Environmental conditions directly affect material selection, protection methods, and long-term reliability.

Must Include:

  • Operating temperature range (min/max)
  • Humidity and moisture exposure
  • Chemical exposure (oils, fuels, solvents)
  • Vibration and mechanical stress levels
  • UV exposure (outdoor applications)
Common Mistake: Not mentioning that the harness will be near heat sources or exposed to hydraulic fluid. This leads to premature insulation failure.
Pro Tip: Map the actual environment. Measure temperatures, document chemical exposures, and specify accordingly. "Industrial environment" is too vague.
8

IP Rating and Sealing Requirements

Ingress Protection ratings determine connector and cable sealing requirements for moisture and dust resistance.

Must Include:

  • Required IP rating (IP65, IP67, IP68)
  • Specific sealing requirements
  • Connector sealing (sealed vs. unsealed mating)
  • Cable gland or strain relief specifications
Common Mistake: Specifying IP65 connectors in environments with high-pressure washdowns or submersion. IP65 protects against water jets, not immersion.
Pro Tip: IP67 = temporary immersion (1m, 30min). IP68 = continuous immersion. Know the difference before specifying.
9

Certifications and Compliance

Industry certifications and regulatory compliance requirements that your harness must meet.

Must Include:

  • UL/CSA/CE certification requirements
  • Industry standards (IATF 16949 for automotive, IPC/WHMA-A-620 for workmanship)
  • RoHS/REACH compliance
  • Country-specific requirements
Common Mistake: Assuming all manufacturers meet the same quality standards. Not all suppliers are certified to IATF 16949 or follow IPC/WHMA-A-620.
Pro Tip: IPC/WHMA-A-620 is the only industry-consensus workmanship standard for cable and wire harness assemblies. Require it.

Learn more about IP protection ratings and how they apply to connector selection. For robotics applications with extreme flex requirements, see our Warehouse Robot Cable Guide.

3

Part 3: Commercial Terms

Commercial terms significantly impact pricing and lead times. Clear expectations upfront prevent surprises during production.

10

Quantity and Volume

Order quantity dramatically affects pricing. Be clear about initial orders and annual forecasts.

Must Include:

  • Initial order quantity
  • Annual estimated usage (EAU)
  • Prototype quantity (if applicable)
  • Production ramp-up schedule
VolumeTypical PriceNotes
Prototype (1-100 pcs)$30-$100/pieceHigher per-unit cost, faster turnaround
Low Volume (100-1,000 pcs)$15-$30/pieceSome tooling amortization
Medium Volume (1,000-10,000 pcs)$5-$25/pieceOptimized for efficiency
High Volume (10,000+ pcs)$2-$10/pieceFull automation benefits
Pro Tip: Share your 3-year volume forecast. This helps suppliers offer better pricing and plan capacity.
11

Lead Time Requirements

Be realistic about delivery timelines. Expedited orders cost 25-50% more.

Must Include:

  • Required delivery date
  • Prototype lead time needs
  • Production lead time expectations
  • Expedite requirements (if any)
IndustryTypical Lead TimeNotes
Industrial IoT4-5 weeksRapid prototyping focus
Medical Devices6-8 weeksFDA validation requirements
Automotive8-14 weeksPPAP and qualification
Aerospace12-16 weeksAS9100 documentation
Pro Tip: Wire harness design is often the last step in product development, leaving insufficient lead time. Plan ahead—"less than lead time away" is expensive.
12

Prototype vs. Production

Clarify whether this is a prototype build or production order. Requirements differ significantly.

Must Include:

  • Current project phase (design validation, production)
  • Prototype quantity and timeline
  • Production volume forecast
  • Design freeze status
Common Mistake: Switching manufacturers between prototype and production. This duplicates tooling costs and loses design learning.
Pro Tip: Choose a manufacturer who can support prototype through production. Consistency reduces risk and often saves 20-30% in tooling costs.
13

Testing Requirements

Specify what testing is required and whether 100% testing or sampling is acceptable.

Must Include:

  • 100% test vs. sampling requirements
  • Continuity testing requirements
  • Hi-pot (dielectric withstand) test voltage
  • Pull force testing for crimp connections
  • Functional test requirements
Common Mistake: Skipping 100% electrical testing to save costs. Undetected opens, shorts, and miswires cause field failures that cost 100x more to fix.
Pro Tip: Opens, shorts, and miswires are the three most common defects. 100% continuity testing catches all of them before shipping.
4

Part 4: Supplier Evaluation

A complete RFQ should also specify what you expect from suppliers. This helps manufacturers self-qualify and ensures you receive quotes only from capable sources.

14

Supplier Qualification Requirements

Define what certifications and capabilities you require from potential suppliers.

Must Include:

  • Required certifications (ISO 9001, IATF 16949, ISO 13485)
  • Minimum years of experience
  • Industry experience requirements
  • Quality management system expectations
  • Communication and timezone preferences
Common Mistake: Focusing only on price without evaluating supplier capabilities. The cheapest quote often comes from the least capable supplier.
Pro Tip: Visit the factory or request a virtual tour. See the equipment, meet the team, and verify capabilities before committing.
15

Project Contact Information

Provide clear contact details to enable quick communication and avoid delays.

Must Include:

  • Technical contact (engineering questions)
  • Commercial contact (pricing, terms)
  • Best times to reach you
  • Decision timeline
  • Preferred communication method
Common Mistake: Using multiple communication channels (email, text, fax, phone) without consolidation. This leads to missed information and delays.
Pro Tip: Designate a single point of contact and establish a weekly sync call for complex projects. Clear communication prevents 80% of project issues.

Learn more about supplier qualifications from the Wiring Harness Manufacturer's Association (WHMA) , which establishes industry standards in partnership with IPC .

Top 5 RFQ Mistakes That Cost Time and Money

Based on our experience processing thousands of RFQs, these are the most common mistakes buyers make—and their real costs:

Incomplete Technical Information

Cost: 2-4 weeks delay

Missing drawings, partial BOMs, or vague specifications force suppliers to guess—resulting in inaccurate quotes or multiple rounds of clarification that delay your project by 2-4 weeks.

Unrealistic Tolerance Requirements

Cost: 20-40% cost increase

Applying machining tolerances (±0.001") to wire harnesses. Standard harness tolerance is ±0.5"—tighter specs require special fixtures and add 20-40% to costs.

Ignoring Environmental Factors

Cost: Field failures + recalls

Failing to specify temperature, vibration, or chemical exposure leads to material selection errors. The harness may fail in the field within months.

Price-Only Evaluation

Cost: 10-50x in field failures

Choosing the lowest bidder without evaluating total cost of ownership. Cheap connectors, inadequate testing, and poor quality cost 10-50x more in field failures.

Fragmented Communication

Cost: Errors + delays

Using email, phone, text, and fax with multiple contacts. Information gets lost, specifications get confused, and mistakes multiply.

Real-World Impact: A study by HICX on supplier communication found that fragmented communication channels lead to missed PO acknowledgments, inaccurate delivery dates, and mismatched invoices—all of which cascade into project delays.

Your Complete RFQ Checklist

Use this checklist before submitting any wire harness RFQ to ensure completeness:

Technical Specifications

  • Assembly drawing (2D/3D)
  • Bill of Materials (BOM)
  • Electrical specifications
  • Connector details
  • Wire specifications
  • Tolerance requirements

Environment Requirements

  • Operating temperature range
  • IP rating requirements
  • Certification requirements

Commercial Terms

  • Quantity (initial + annual)
  • Lead time requirements
  • Prototype vs production
  • Testing requirements

Supplier Requirements

  • Required certifications
  • Contact information

Next Steps: Submit Your Complete RFQ

A complete RFQ is the foundation of a successful wire harness project. By including all 15 details covered in this guide, you'll:

  • Receive accurate quotes the first time (no back-and-forth delays)
  • Compare suppliers fairly on an apples-to-apples basis
  • Avoid surprise costs during production
  • Build better relationships with manufacturing partners
  • Get your harnesses faster and with higher quality

At WellPCB, we process RFQs within 24 hours and provide detailed engineering feedback on your specifications. Our team follows IPC/WHMA-A-620 workmanship standards and holds both ISO 9001 and IATF 16949 certifications.

Ready to Get an Accurate Quote?

Submit your RFQ now and receive detailed pricing, DFM feedback, and lead time confirmation within 24 hours.

Related Resources

🔗 Cable Assembly vs Wire Harness - Understanding the differences

🔗 Wire Harness Design Guide - 10 critical steps for engineers

🔗 Our Manufacturing Capabilities - Equipment and certifications

🔗 UL Certification - Safety certification standards

🔗 RoHS Directive - EU compliance requirements