ISO 7638-1:2018

Overview

ISO 7638-1:2018 specifies dimensional, electrical and mechanical requirements for connectors used to link braking systems and running gear between towing and towed vehicles with a 24 V nominal supply voltage. The standard defines plug, socket and park-socket dimensions, contact allocation and designation, terminal and cable sizes, and test requirements (mating, endurance, connection/disconnection forces). It ensures reliable electrical connections for trailer braking and running-gear functions and provides guidance for component design, assembly and testing.

Key Topics and Technical Requirements

• Dimensional characteristics
  • Defined geometries for plug, socket and park socket; cover and locking lever design requirements. (Certain unspecified details left to manufacturer discretion.)
  • Park socket intended to receive and store the plug when disconnected; cover closes automatically.
  • Locking lever maximum distance requirement for interchangeability.
• Contact allocation and designation
  • A 7-contact allocation for brake/running-gear functions (contacts 1–7), including Plus electrovalve, Plus/Minus electronics, Warning device, CAN_H and CAN_L for data exchange.
  • Contact numbers must be permanently marked on the inside of the socket cover and terminal faces (character height ≥ 2 mm where space permits).
• Terminals and connecting cable
  • Rear terminals accept specified conductor sizes: Contacts 1 & 4 - 4 mm²; Contacts 2, 3, 5, 6 & 7 - 1.5 mm² (other sizes by agreement).
  • Connecting cables must meet applicable parts of ISO 4141.
• Mechanical and electrical tests
  • Compliance with ISO 4091 test procedures unless otherwise specified.
  • Mismating prevention: connectors must not mate with ISO 12098 or ISO 7638-2 connectors without excessive force.
  • Connection/disconnection force: shall not exceed 35 N (per ISO 4091 test).
  • Endurance: tested for 10 000 cycles.
• Design details
  • Contacts shall be floating and self-aligning on engagement.
  • Sealing ring mounting and smooth, burr-free areas are specified for durability and sealing.

Applications and Who Uses This Standard

• Vehicle manufacturers (OEMs) and trailer builders specifying trailer-to-towing vehicle electrical interfaces for braking and running gear.
• Connector and cable suppliers designing 24 V trailer connectors, park sockets and coiled/uncoiled cable assemblies.
• Test laboratories and quality engineers performing conformity and endurance testing.
• Systems integrators implementing CAN-based braking communication (reference ISO 11992 series).
• Regulatory and procurement teams requiring standards-based compatibility across fleets.

Related Standards

• ISO 7638-2 - same family for 12 V systems.
• ISO 12098 - 15‑pole connector for 24 V vehicles (mating considerations).
• ISO 4091 - general connector tests and requirements (referenced test methods).
• ISO 4141 - multi-core connecting cables.
• ISO 11992-1 / ISO 11992-2 - digital data interchange for brakes and running gear.

Keywords: ISO 7638-1:2018, connectors for towing and towed vehicles, 24 V trailer connector, braking system connector, park socket, contact allocation, connector endurance test.