How to design and develop automotive wiring harnesses

Classification of car wires

American Standard Automotive Wires (SAE J1128, J1939, etc.)

• Governing Body: SAE (Society of Automotive Engineers)

• Common Types: GPT, GXL, TXL, SXL

• Features:

  • Rated for 60–125°C, depending on insulation type

  • Insulation is typically made of PVC or cross-linked polyethylene

  • Conductor size in AWG (American Wire Gauge)

  • Widely used in North America

Applications: General wiring (GPT), high-temp areas (GXL, TXL), and commercial vehicles (SXL).

German Standard Automotive Wires (DIN/ISO standards, LV 112)

• Governing Body: DIN, ISO, and OEM-specific standards (e.g., VW, BMW)

• Common Types: FLRY-A, FLRY-B, FLY, FKS, etc.

• Features:

  • Thin-wall PVC insulation, space-saving

  • Temperature rating usually 105–125°C

  • Metric wire sizes (e.g., 0.5 mm², 1.0 mm²)

  • Excellent flame resistance and flexibility

  • LV 112 specifies performance for modern car networks

Applications: Widely used in European cars for body, engine, and CAN/LIN networks.

Japanese Standard Automotive Wires (JASO/DENSO standards)

• Governing Body: JASO (Japanese Automotive Standards Organization), DENSO, etc.

• Common Types: AV, AVS, AVSS, CAVUS

• Features:

  • Very thin-wall insulation (especially AVSS)

  • Temperature rating ~85–120°C

  • Metric sizes (e.g., 0.3 mm², 0.5 mm²)

  • Lightweight, compact for space-constrained Japanese vehicles

Applications: Common in Japanese vehicles for dashboards, ECUs, and tight routing.

Selection Tips:

• Match the OEM standard if replacing parts in a specific brand (e.g., use FLRY in BMW).

• Consider temperature, voltage, chemical exposure, and space constraints.

• Choose SAE for North America, DIN/ISO for European cars, and JASO for Japanese vehicles

How to choose the right car wires

Determine the Application Environment

• Engine bay: High temp (up to 125–150°C), oil/fuel resistant → use GXL, TXL, FLRY-B, or cross-linked wires

• Cabin/interior: Lower temp, less stress → GPT, AV, AVS

• Chassis/underbody: Exposure to water, abrasion → use shielded or reinforced insulation

Choose the Correct Wire Standard

• SAE (e.g., GXL, SXL, TXL): Ideal for North American vehicles

• DIN/ISO (e.g., FLRY, FLY): Common in European vehicles

• JASO (e.g., AVSS, CAVUS): Suited for Japanese vehicles

Use the same standard as the vehicle manufacturer to ensure compatibility and safety.

Select Proper Insulation Material

• PVC (e.g., GPT, FLRY-A): Cost-effective, general use, up to ~105°C

• Cross-linked Polyethylene (e.g., GXL, TXL): Higher temp (125–150°C), better chemical resistance

• Silicone or Teflon: Extreme temp or high flexibility needs (less common in standard cars)

Calculate Current Load and Choose Wire Gauge

• Match wire gauge (AWG or mm²) to the current draw:

  • E.g., 0.5 mm² or 20 AWG for small signals

  • 4 mm² or 12 AWG for higher current devices (like fans or fog lights)

Use charts to avoid overheating or voltage drop.

 Consider Voltage Rating

• Most car systems: 12V or 24V

• Choose wires rated ≥ system voltage with margin (usually ≥60V rating for insulation)

Additional Considerations

• Color coding: Helps with troubleshooting and standardization

• Flexibility: Thin-wall wires (e.g., TXL, AVSS) are better for tight routing

• Shielding: Needed for sensitive signal wires (e.g., CAN bus)

Summary Chart:

How to design and develop automotive wiring harnesses and match automotive wires

System Requirements Analysis

• Define vehicle electrical architecture (12V, 24V, HV systems)

• Identify all electronic components: ECUs, sensors, actuators, lights, infotainment, etc.

• Gather current, voltage, and communication needs for each component

Circuit and Wiring Diagram Design

• Create functional block diagrams, followed by schematic circuit diagrams

• Include:

  • Power supply routing

  • Grounding points

  • Signal paths (e.g., CAN, LIN, Ethernet)

  • Fuse and relay locations

Use ECAD software like Zuken E3.series, Mentor Capital, or CATIA Electrical.

Wire Selection and Matching

Select wire type for each circuit based on:

Also, select color codes and labeling schemes for easy service.

Harness Architecture Design

• Design branch structure: main trunk + sub-branches

• Determine:

  • Wire lengths

  • Connector types (sealed/unsealed, pin count)

  • Routing paths (based on vehicle 3D CAD layout)

• Consider:

  • Bend radius

  • Mounting clips

  • Protection (tapes, sleeves, convoluted tubes)

Use 3D harness design tools integrated with vehicle CAD (e.g., CATIA Harness, Siemens NX).

Prototyping and Testing

• Build a prototype using real components

• Conduct tests:

  • Electrical: continuity, insulation resistance, voltage drop

  • Mechanical: vibration, abrasion, connector fit

  • Environmental: temperature cycling, fluid exposure, corrosion

Manufacturing Preparation

• Prepare bill of materials (BOM), wiring tables, and cutting lists

• Use automated machines for wire cutting, stripping, crimping

• Document work instructions for assembly and QC

Final Validation and Compliance

• Perform system integration in the vehicle

• Validate against standards: ISO 6722, LV 112, SAE J1939, etc.

• Ensure compliance with OEM-specific requirements (VW, Toyota, etc.)

Requirements → Schematics → Wire Selection → 3D Routing → Prototype → Test → Manufacture