Overview
ISO 1185:2003 specifies the physical and functional requirements for the 7‑pole 24 N connector used for the electrical connection between towing and towed vehicles with a 24 V nominal supply voltage. The standard defines dimensions, contact allocation, mechanical and environmental tests, and marking requirements to ensure interchangeability and safe operation of trailer/tow vehicle electrical interfaces.
Key topics and technical requirements
- Connector type and layout
- Defines a 7‑pole plug and socket: six smaller spring tubes/pins (Contacts 2–7) plus one larger tube/pin (Contact 1).
- Dimensional drawings (plug and socket) determine form, pitch circle and locking features to ensure physical compatibility.
- Contact allocation and wire colours
- Contact functions and recommended core insulation colours:
- 1 - Common return (White)
- 2 - Left‑hand rear position & registration plate illumination (Black)
- 3 - Left‑hand direction indicator (Yellow)
- 4 - Stop lights (Red)
- 5 - Right‑hand direction indicator (Green)
- 6 - Right‑hand rear position & registration plate illumination (Brown)
- 7 - Braking control for trailers (Blue)
- Note: rear registration plate lamps shall not share a common connection to both contacts 2 and 6.
- Electrical and mechanical terminals
- Rear terminals accept nominal conductor cross‑sections: Contact 1 = 2.5 mm²; Contacts 2–7 = 1.5 mm².
- Contact identification must be permanently marked inside the socket cover and on terminal faces (character size ≥ 2 mm, smaller allowed where space is limited).
- Identification and protection
- 24 N connectors must be distinguished from 24 S by darker permanent colouring (preferably black).
- A storage/protection provision for a disconnected plug is required to prevent ingress of water and damage.
- Tests and performance
- Test sequences reference ISO 4091 with specific requirements: mismating prohibition (no contact between Contact 1 and Contacts 2–7), locking/cable retention force 500 ±5 N, connection/disconnection force 150 ±50 N, modified temperature/humidity cycling (−25 °C to 75 °C), salt spray and endurance (1 000 cycles) as specified.
Applications and users
- Intended for heavy commercial vehicles, trailers, semi‑trailers, drawbar trailers and towing vehicles requiring standardized 24 V electrical interconnection.
- Primary users:
- Vehicle manufacturers and OEMs
- Trailer and connector component suppliers
- Fleet operators, maintenance engineers and vehicle inspectors
- Test laboratories validating connector compliance
- Practical benefits: ensures plug/socket interchangeability, safer trailer lighting/braking connections, simplified maintenance and global compatibility.
Related standards
- ISO 3731 - 7‑pole connector type 24 S (supplementary)
- ISO 12098 - 15‑pole connector (alternative for >7 functions)
- ISO 4091 - Definitions, tests and requirements for towing/towed connectors
- ISO 4009 - Location of electrical/pneumatic connections
- ISO 4141 - Multi‑core connecting cables
Keywords: ISO 1185, 7‑pole connector, 24 N, 24 V, towing and towed vehicles, contact allocation, trailer connector, connector dimensions, electrical connector standard.