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.
Open preview (PDF)Road vehicles — Connectors for the electrical connection of towing and towed vehicles — 7-pole connector type 12 N (normal) for vehicles with 12 V nominal supply voltage