Automotive Wire Types: SAE J1128 vs ISO 6722
Decoding the acronyms and selecting the right primary cable for North American and European architectures.
Primary wire is the circulatory system of the vehicle. Specifying the wrong wire type leads to premature insulation failure, excessive weight, or manufacturing difficulties. Global sourcing requires understanding both North American (SAE) and European (ISO/DIN) nomenclatures.
SAE J1128 (North American Standard)
The Society of Automotive Engineers (SAE) standard J1128 defines low-voltage primary cable. The nomenclature identifies the insulation material and the wall thickness.
| Type | Insulation | Wall Thickness | Temp Rating | Primary Use Case |
|---|---|---|---|---|
| GPT | PVC | Standard | 85°C | General cabin wiring, aftermarket audio. |
| TWP | PVC | Thin | 105°C | Cabin wiring where space is limited. |
| SXL | Cross-linked (XLPE) | Standard | 125°C | Engine compartments, high abrasion areas. |
| GXL | Cross-linked (XLPE) | Thin | 125°C | Most common engine bay wire; balances toughness and size. |
| TXL | Cross-linked (XLPE) | Extra Thin | 125°C | Modern high-density harnesses (ECU connectors). |
ISO 6722 (European / DIN Standard)
European OEMs utilize the ISO 6722 standard (often referring to DIN 72551 for older designs). The naming convention (FLRY) provides specific structural information.
- FL: Automotive low-tension cable (Fahrzeugleitung)
- R: Reduced wall thickness
- Y: PVC insulation (Thermoplastic)
- X: XLPE insulation (Cross-linked)
- W: High heat resistant
Common Examples:
- FLRY: Reduced wall PVC (similar to TWP). The standard for European cabin wiring.
- FLRYW: Reduced wall high-temp PVC.
- FLR2X: Reduced wall XLPE (similar to GXL/TXL). Used in engine bays.
Stranding: Type 1 vs Type 2 vs Type 3
Regardless of insulation, the copper core's flexibility matters.
- Type 1 (Concentric): Fewer, thicker strands. Stiffer. Used for straight runs.
- Type 2 (Bunched): Standard flexibility. Good for most harness routing.
- Type 3 (High-Strand): Many very fine strands. Highly flexible. Required for areas with constant movement (e.g., door hinges, robot arms).
Sourcing Considerations
While a 1.0mm² FLRY cable and an 18 AWG TWP cable are functionally very similar in current carrying capacity, they are not directly interchangeable in manufacturing. The slight difference in outer diameter means they require different crimp tooling and different connector seals.
Converting AWG to mm²?
Use our interactive tool to accurately translate North American gauge sizes to European metric equivalents, including correct ampacity derating.
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