ISO 1724:2003

Overview

ISO 1724:2003 defines the mechanical and electrical requirements for the 7‑pole connector type 12 N used for the electrical connection between towing and towed vehicles with a 12 V nominal supply voltage. The standard specifies connector dimensions, contact allocation, marking and wiring details, and a sequence of tests to ensure interchangeability and reliable operation in vehicle towing applications.

Keywords: ISO 1724:2003, 7‑pole connector, 12 N, 12 V, towing and towed vehicles, electrical connector, interchangeability

Key topics and technical requirements

• Dimensions and construction
  • Detailed plug and socket geometry to ensure compatibility (pins slotted for ≥8.5 mm compression).
  • Socket cover that closes automatically when unplugged.
• Contact allocation and wiring
  • Seven contacts with defined functions and insulation colours:
    • 1 - Left indicator (Yellow)
    • 2 - Rear fog light (Blue)
    • 3 - Common return (White)
    • 4 - Right indicator (Green)
    • 5 - Right rear position/plate illumination (Brown)
    • 6 - Stop lights (Red)
    • 7 - Left rear position/plate illumination (Black)
  • Terminal cross-sections: contacts 1,2,4,5,6,7 accept 1.5 mm²; contact 3 accepts 2.5 mm².
• Marking and identification
  • Contact numbers permanently marked on terminal faces and inside socket cover (character height ≥2 mm where space allows).
  • 12 N connectors distinguished from 12 S by a dark, permanent insulating colour (preferably black).
• Performance and tests
  • Test sequences referenced to ISO 4091 (visual, dimensional, connection/disconnection, current cycling, salt spray, temperature/humidity cycling, endurance).
  • Connection force ≤ 200 N; disconnection force between 50 N and 200 N.
  • Cable retention test: 250 ± 5 N applied to disengaged plug retention.
  • Modified environmental tests: temperature cycling includes −25 °C to +75 °C; endurance for 1 000 cycles.
  • Salt spray and other tests per ISO 4091 with specified exceptions.

Applications and users

• Vehicle OEMs (cars, light commercial vehicles) and trailer manufacturers specifying standard towing electrical interfaces.
• Connector and cable harness suppliers designing components for trailer/towbar systems.
• Aftermarket trailer accessory makers, fleet operators, and testing laboratories validating compliance and interchangeability.
• Regulatory and conformity bodies referencing consistent wiring and connector dimensions for safety and compatibility.

Related standards

• ISO 3732 - 7‑pole connector type 12 S (supplementary)
• ISO 11446 - 13‑pole connector (alternative for more circuits)
• ISO 4091 - Definitions, test methods and requirements for towing connectors
• ISO 4141 - Multi‑core connecting cables
• ISO 1103 - Mechanical coupling dimensions for compatibility

For design, manufacturing or compliance activities, consult the full ISO 1724:2003 text and referenced ISO documents for complete drawings, tolerances and test procedures.