ISO 7638-2:2018

Overview

ISO 7638-2:2018 specifies connectors for the electrical connection of braking systems and running gear of towing and towed road vehicles with a 12 V nominal supply voltage. The standard defines dimensional characteristics, contact allocation, marking, terminal sizes, and required tests - including a dedicated park socket to receive and store the plug when disconnected. It ensures safe, reliable, and interchangeable electrical connections between tractors and trailers for brake control and related systems.

Key topics and technical requirements

• Dimensions & mechanical design
  • Defined geometries for plug, socket and park socket (locking lever, cover, sealing ring).
  • Contacts are floating and align to a datum position on engagement.
  • Park socket cover must close automatically when the plug is disconnected.
• Contact allocation (7‑pole connector)
  • 1: Plus electrovalve
  • 2: Plus electronics
  • 3: Minus electronics
  • 4: Minus electrovalve
  • 5: Warning device (open circuit in normal operation)
  • 6: CAN_H
  • 7: CAN_L
• Terminals and cables
  • Rear terminals accept cables with nominal cross-sections:
    • Contacts 1 and 4: 4 mm²
    • Contacts 2, 3, 5, 6, 7: 1.5 mm²
  • Connecting cables shall meet applicable parts of ISO 4141.
• Tests and performance
  • Test regime referenced to ISO 4091 with specific deviations:
    • Endurance: 10 000 mating cycles.
    • Connection/disconnection force: ≤ 35 N.
    • Mismating: must prevent interconnection with connectors conforming to ISO 12098 and ISO 7638-1 without excessive force.
  • Contact designation numbers permanently marked on socket cover and terminal faces.

Applications and who uses it

ISO 7638-2:2018 is used by:

• Vehicle and trailer manufacturers (design and integration of braking/running-gear electrical interfaces)
• Connector and cable suppliers (component design and verification)
• Automotive electrical system engineers and OEMs (ensuring interoperability)
• Test laboratories and quality teams (type approval and endurance testing)
• Fleet operators and maintenance engineers (replacement, retrofit, and safe handling)

Practical applications include specifying connector dimensions for manufacturing, ensuring correct CAN and warning device wiring, selecting appropriate cable cross-sections, and validating durability and safety of trailer-to-towing vehicle electrical links.

Related standards

• ISO 4091 - Definitions, tests and requirements for towing/towed vehicle connectors
• ISO 4141 (parts) - Multi-core connecting cables
• ISO 11992-1 / -2 - Digital interchange for brakes and running gear (physical/data-link/application layers)
• ISO 12098 - 15‑pole connector for 24 V systems
• ISO 7638-1 - Other parts of the ISO 7638 series

Keywords: ISO 7638-2:2018, connectors for braking systems, 12 V connectors, towing and towed vehicles, contact allocation, park socket, CAN_H, CAN_L, endurance test.