Electrical coils with plugs
Spiral cables with factory-fitted plugs form a fundamental part of the electrical connection between tractor and trailer in heavy road transport. They carry lighting signals, brake system data and supply voltage under the mechanical and climatic stress that is inherent to professional haulage operations. Selecting the correct spiral cable depends primarily on the applicable norm, the number of poles, the operating voltage and the specific function the cable fulfils within the vehicle combination.
The most widely applied standards in this product group are ISO 7638, ISO 1185, ISO 3731, ISO 11446 and ISO 12098. Each of these standards defines the electrical and mechanical requirements that both the plug connection and the cable itself must satisfy. ISO 7638 is the international standard for connecting ABS and EBS systems between tractor and trailer. A 7-pin spiral cable truck that complies with ISO 7638 carries both the supply voltage and the CAN-bus signals required for the full operation of electronic braking systems. In combinations equipped with Euro 6 drivetrains, this connection is mandatory and technically decisive for the braking system integration of the entire combination.
For lighting connections, different standards apply. ISO 1185, also referred to as Type N, governs the 7-pin connection for standard lighting functions on 24-volt systems. This standard applies to spiral cables that control brake lights, indicators, rear lights and marker lighting on the trailer. The EBS spiral cable ISO 7638 and the Type N lighting cable compliant with ISO 1185 therefore fulfil complementary functions within the same vehicle combination. ISO 3731, known as Type S, is the counterpart of ISO 1185 but is intended for trailers with additional signal requirements. A spiral cable with plug trailer that complies with ISO 3731 accommodates extra functions beyond basic lighting signals and is frequently used in Euro 6 combinations.
For applications requiring more contacts, 13-pin cables compliant with ISO 11446 and 15-pin cables compliant with ISO 12098 are available. The 13-pin standard is the most widely used in Europe for trailers that require a 12-volt auxiliary supply in addition to lighting. ISO 12098 provides a 15-pin connection sufficient for heavier trailers with more extensive electrical systems, such as combinations with ABS, EBS and additional power take-off. An adapter cable converting ISO 12098 to two separate 7-pin connections in accordance with ISO 1185 and ISO 3731 also allows modern 15-pin systems to remain compatible with vehicles still equipped with the individual 7-pin sockets.
A technically relevant distinction within this category concerns the sealing of the plug connection. Vulcanised plugs provide a permanent, watertight connection that does not rely on separate sealing rings or clamps. The vulcanisation process bonds the plug and cable sheath at the molecular level, fully sealing the transition against moisture, dust and corrosive substances. This is significant given the demanding conditions of long-distance international transport combinations, where the electrical connection between tractor and trailer is subjected daily to coupling and uncoupling cycles, road contamination and temperature fluctuations. Some manufacturers apply additional sealing technology that provides a further improvement in water resistance, even during prolonged exposure to spray and rain water.
The 7-pin spiral cable truck in versions compliant with ISO 7638 is increasingly available with ADR certification, enabling its use in combinations transporting hazardous goods. Such transports are subject to additional technical requirements for the electrical equipment of the vehicle, including the spiral cable itself. The standard requires that the cable continues to function reliably under exceptional load conditions and does not pose a risk to the electrical installation of the combination.
Working lengths for spiral cables with plugs in this category vary, with extended lengths of up to 4.5 metres available for combinations where greater distances between the contact points of tractor and trailer must be bridged. The spiral construction ensures the cable retracts automatically when no tensile force is applied, preventing sagging and premature wear caused by contact with the road surface or the chassis frame.
In the daily operations of trailer builders, body builders, coachbuilders and truck workshops, the spiral cable with plug trailer is a standard component applied at every new build or overhaul of a trailer. The combination of the correct standard, the appropriate number of poles and a robust plug construction determines the reliability of the electrical connection across the full service life of the vehicle combination. Wholesalers and transport companies with in-house workshops select spiral cables that align with the standards applicable to their fleet, ensuring interchangeability and ease of maintenance.