I Introduction
We need to make sure that all the wiring from the truck car to the trailer is functioning properly when we try to take matters into our own hands and replace and upgrade our own trailer wiring. If you connect any of the wires incorrectly it is highly likely that you will have an accident.
In this blog I will go over the trailer wiring connections according to each national standard. I’ll also go back and analyze the details you need to pay attention to when wiring between different standards.
II Standard Overview Table
| Standard | Voltage | Connector | Country | Cable Size |
| ISO 1724 | 12v | 7 Pin Round | EU UK Light Duty Trailer | 6×1.5mm2+1×2.5mm2 |
| ISO 3732 | 12v | 7 Pin Round | EU UK Light Duty Trailer | 4×1.5mm2+3×2.5mm2 |
| ISO 1185 | 24v | 7 Pin Round | EU UK Heavy Duty Trailer | 6×1.5mm2+1×2.5mm2 |
| ISO 3731 | 24v | 7 Pin Round | EU UK Heavy Duty Trailer | 4×1.5mm2+3×2.5mm2 |
| SAE J560 Primary | 12v | 7 Pin Round | North America | 12/4 + 10/2 + 8 awg |
| SAE J560 Auxiliary | 12v | 7 Pin Round | North America | 12/4 + 10/2 + 8 awg |
| SAE J2863 | 12v | 7 Pin Round | North America | 14/4 + 12 +10/2 awg |
| AS 4735 | 12v | 7 Pin Round | AU and NZ | 6×1.5mm2+1×2.5mm2 |
| AS 2513 | 12v | 7 Pin Round | AU and NZ | 6×1.5mm2+1×2.5mm2 |
| ISO 7638-1(2) | 24v(12v) | 7 Pin Round | EU UK Heavy Duty Trailer | 5x 1.5mm2 + 2x 4mm2 |
| ISO 11446 | 12v(24v) | 13 Pin Round | EU UK Heavy Duty Trailer | 5x 2.5mm2 + 8x 1.5mm2 |
| ISO 12098 | 24v | 15(13) Pin Round | EU UK Heavy Duty Trailer | 3x 2.5mm2 + 12x 1.5mm2 |
III Trailer Wiring Details
1. ISO 1724 12N Trailer Wiring
| Contact No. | Function | Cross-sectional area | Core Wire Color |
| 1 | Left-hand direction indicator light | 1.5mm2 | Yellow |
| 2 | Rear fog light | 1.5mm2 | Blue |
| 3 | Common return | 2.5mm2 | White |
| 4 | Right-hand direction indicator light | 1.5mm2 | Green |
| 5 | Right-hand rear position and marker lights, and rear registration plate illumination device | 1.5mm2 | Brown |
| 6 | Stop light | 1.5mm2 | Red |
| 7 | Left-hand rear position and marker lights and rear-registration-plate illumination device | 1.5mm2 | Black |
# The rear registration plate illumination device shall be connected such that no lamp of the device has a common connection with both contacts 5 and 7
Cable Type Recommend
- Cable Sheath: PVC or PUR (Preferred)
- Cable Size: 6×1.5mm2+1×2.5mm2 (Standard) or 6x1mm2+1×1.5mm2 (economical)
Connectors Recommend
- Plug: ISO1724 12N Reinforced Composite Plug / Silver Metal Plug
- Socket: ISO1724 12N Reinforced Composite Socket / Silver Metal Socket
2. ISO 3732 12S Trailer Wiring
| Contact No. | Function | Cross-sectional area | Core Wire Color |
| 1 | Common return | 2.5mm2 | White |
| 2 | Reserved for future allocation | 1.5mm2 | Black |
| 3 | Reversing light | 1.5mm2 | Yellow |
| 4 | Permanent Power Supply | 2.5mm2 | Red |
| 5 | Sensing Device with common return | 1.5mm2 | Green |
| 6 | Power supply controlled by ignition switch | 2.5mm2 | Brown |
| 7 | Rear fog light | 1.5mm2 | Blue |
# The rear registration plate illumination device shall be connected such that no lamp of the device has a common connection with both contacts 2 and 6
Cable Type Recommend
- Cable Sheath: PVC PUR (Preferred)
- Cable Size: 4×1.5mm2+3×2.5mm2
Connectors Recommend
- Plug: ISO3732 12S Reinforced Composite Plug / Silver Metal Plug
- Socket: ISO3732 12S Reinforced Composite Socket / Silver Metal Socket
3. ISO 1185 24N Trailer Wiring
| Contact No. | Function | Cross-sectional area | Core Wire Color |
| 1 | Common return | 2.5mm2 | White |
| 2 | Left-hand rear position and marker lights, and rear registration plate illumination device | 1.5mm2 | Black |
| 3 | Left-hand direction indicator light | 1.5mm2 | Yellow |
| 4 | Stop lights | 1.5mm2 | Red |
| 5 | Right-hand direction indicator light | 1.5mm2 | Green |
| 6 | Right-hand rear position and marker lights, and rear registration plate illumination device | 1.5mm2 | Brown |
| 7 | Braking control for trailers | 1.5mm2 | Blue |
Cable Type Recommend
- Cable Sheath: PVC or PUR (Preferred)
- Cable Size: 6×1.5mm2+1×2.5mm2 (Standard) or 6x1mm2+1×1.5mm2 (economical)
Connectors Recommend
- Plug: ISO1185 24N Reinforced Composite Plug / Alu/ Zinc alloy Plug(with Spring is preferred)
- Socket: ISO1185 24N Reinforced Composite Plug / Alu/ Zinc alloy Socket
4. ISO 3731 24S Trailer Wiring
| Contact No. | Function | Cross-sectional area | Core Wire Color |
| 1 | Common return | 2.5mm2 | White |
| 2 | Reserved for future allocation | 1.5mm2 | Black |
| 3 | Reversing light | 1.5mm2 | Yellow |
| 4 | Permanent power supply | 2.5mm2 | Red |
| 5 | Sensing device with common return | 1.5mm2 | Green |
| 6 | Power supply controlled by ignition switch | 2.5mm2 | Brown |
| 7 | Rear fog light | 1.5mm2 | Blue |
Cable Type Recommend
- Cable Sheath: PVC or PUR (Preferred)
- Cable Size: 4×1.5mm2+3×2.5mm2
Connectors Recommend
- Plug: ISO3731 24S Reinforced Composite Plug / Alu/ Zinc alloy Plug (with Spring is preferred)
- Socket: ISO3731 24S Reinforced Composite Plug / Alu/ Zinc alloy Socket
5. SAE J560 Primary Trailer Wiring
| Contact No. | Function | Cross-sectional area | Core Wire Color |
| 1 | Ground return to towing vehicle | 8awg 8mm2 | White |
| 2 | Clearance side marker and identification lamps | 12awg 3mm2 | Black |
| 3 | Left turn signal and hazard lamps | 12awg 3mm2 | Yellow |
| 4 | Stop lamps and anti-lock braking system | 10awg 5mm2 | Red |
| 5 | Right turn signal and hazard lamps | 12awg 3mm2 | Green |
| 6 | Tail and license plate clearance and or side marker lamps | 12awg 3mm2 | Brown |
| 7 | Continuous ABS Primary power/(auxiliary device) | 10awg 5mm2 | Blue |
Cable Type Recommend
- Cable Sheath: PVC or PUR (Preferred)
- Cable Gauge: 12/4 + 10/2 + 8
Connectors Recommend
- Plug: SAE J560 24N Alu/ Zinc alloy Plug(with Spring is preferred)
- Socket: SAE J560 24N Alu/ Zinc alloy Socket
6. SAE J560 Auxiliary Trailer Wiring
| Contact No. | Function | Cross-sectional area | Core Wire Color |
| 1 | Ground Return to towing vehicle | 8awg 8mm2 | White |
| 2 | Cab switched auxiliary power | 12awg 3mm2 | Black |
| 3 | ABS Malfunction signal to cab | 12awg 3mm2 | Yellow |
| 4 | Constant or ignition auxiliary power | 10awg 5mm2 | Red |
| 5 | Unassigned | 12awg 3mm2 | Green |
| 6 | Unassigned | 12awg 3mm2 | Brown |
| 7 | Unassigned | 10awg 5mm2 | Blue |
Cable Type Recommend acc. to SAE J2394
- Cable Sheath: PVC or PUR (Preferred)
- Cable Gauge: 12/4 + 10/2 + 8
Connectors Recommend
- Plug: SAE J560 24N Alu/ Zinc alloy Plug (with Spring is preferred)
- Socket: SAE J560 24N Alu/ Zinc alloy Socket
7. SAE J2863 Trailer Wiring
| Contact No. | Function | Cross-sectional area | Core Wire Color |
| 1 | Left turn signal and hazard lamps | 14awg 2mm2 | Yellow |
| 2 | Ground return to towing vehicle | 12awg 3mm2 | White |
| 3 | Continuous ABS Primary power/(auxiliary device) | 10awg 5mm2 | Blue |
| 4 | Right turn signal and hazard lamps | 14awg 2mm2 | Green |
| 5 | +12 volt | 10awg 5mm2 | Red |
| 6 | rear position and marker lights and rear-registration-plate illumination device | 14awg 2mm2 | Brown |
| 7 | Reverse lights | 14awg 2mm2 | Purple |
Cable Type Recommend
- Cable Sheath: PVC or PUR (Preferred)
- Cable Gauge: 14/4 + 12 +10/2
Connectors Recommend
- Plug: SAE J2863 24N Reinforced Composite Blade Plug (with Spring is preferred)
- Socket: SAE J2863 24N Reinforced Composite Blade Socket
8. AS 4735 Trailer Wiring
| Contact No. | Function | Cross-sectional area | Core Wire Color |
| 1 | Left turn signal | 1.5mm2 | Yellow |
| 2 | Common Earth Return | 2.5mm2 | White |
| 3 | Reversing Lights | 1.5mm2 | Blue |
| 4 | Right turn signal | 1.5mm2 | Green |
| 5 | Stop lights | 1.5mm2 | Red |
| 6 | Right-hand rear position, clearance and marker lamps | 1.5mm2 | Brown |
| 7 | Left-hand rear position, clearance and marker lamps | 1.5mm2 | Black |
Cable Type Recommend
- Cable Sheath: PVC or PUR (Preferred)
- Cable Size: 6×1.5mm2+1×2.5mm2 (Standard) or 6x1mm2+1×1.5mm2 (economical)
Connectors Recommend
- Plug: AS 4735 Reinforced Composite Plug / Alu/ Zinc alloy Plug (with Spring parts is preferred)
- Socket: AS 4735 Reinforced Composite Plug / Alu/ Zinc alloy Socket
9. AS 2513 Trailer Wiring
| Contact No. | Function | Cross-sectional area | Core Wire Color |
| 1 | Common return | 2.5mm2 | White |
| 2 | Reserved for future allocation | 1.5mm2 | Black |
| 3 | Left hand indicator | 1.5mm2 | Yellow |
| 4 | Stop | 1.5mm2 | Red |
| 5 | Right hand indicator | 1.5mm2 | Green |
| 6 | Number plate Markers | 1.5mm2 | Brown |
| 7 | Reserve Signal | 1.5mm2 | Blue |
Cable Type Recommend
- Cable Sheath: PVC or PUR (Preferred)
- Cable Size: 6×1.5mm2+1×2.5mm2 (Standard) or 6x1mm2+1×1.5mm2 (economical)
Connectors Recommend
- Plug: AS 2513 Reinforced Composite Plug / Alu/ Zinc alloy Plug (with Spring parts is preferred)
- Socket: AS 2513 Reinforced Composite Plug / Alu/ Zinc alloy Socket
10. ISO 7638-2 / ISO 7638-1 Trailer Wiring
| Contact No. | Function | Cross-sectional area | Core Wire Color |
| 1 | +12v(24v) Permanent for control valves | 4mm2 | Red |
| 2 | +12v(24v) via ignition lock for electronic | 1.5mm2 | Black |
| 3 | Ground for electronics | 1.5mm2 | Yellow |
| 4 | Ground for control valves | 4mm2 | Brown |
| 5 | ABS Fault indication Warning device | 1.5mm2 | White |
| 6 | CAN H, for EBS and ABS | 1.5mm2 | Green/White |
| 7 | CAN L, for EBS and ABS | 1.5mm2 | Brown/white |
Cable Type Recommend
- Cable Sheath: PVC or PUR (Preferred)
- Cable Size: 5x 1.5mm2 + 2x 4mm2 or 5x 1.5mm2 + 2x 6mm2
Connectors Recommend
- Plug: ISO 7638-2(1) Reinforced Composite Plug
- Socket: ISO 7638-2(1) Reinforced Composite Socket
11. ISO 11446 Trailer Wiring
| Contact No. | Function | Cross-sectional area | Core Wire Color |
| 1 | Left-hand direction indicator light | 1.5mm2 | Yellow |
| 2 | Rear fog light | 1.5mm2 | Blue |
| 3 | Common return for contacts no.1 to 8 | 2.5mm2 | White |
| 4 | Right-hand direction indicator light | 1.5mm2 | Green |
| 5 | Right-hand rear, position, and marker light, and license plate lamp | 1.5mm2 | Brown |
| 6 | Brake light | 1.5mm2 | Red |
| 7 | Left-hand rear, position, and marker lights, and license plate lamp | 1.5mm2 | Black |
| 8 | Reversing light | 1.5mm2 | Pink |
| 9 | Power supply (steady constant) | 2.5mm2 | Orange |
| 10 | Power supply controlled by ignition switch | 2.5mm2 | Grey |
| 11 | Common return for contact no. 10 | 2.5mm2 | White/black |
| 12 | Reserved for future allocation | 1.5mm2 | Light Grey |
| 13 | Common return for contact no.9 | 2.5mm2 | White/red |
Cable Type Recommend
- Cable Sheath: PVC or PUR (Preferred)
- Cable Size: 5x 2.5mm2 + 8x 1.5mm2
Connectors Recommend
- Plug: ISO11446 Reinforced Composite Plug or (with Spring parts is preferred)
- Socket: ISO11446 Reinforced Composite Socket
12. ISO 12098 Trailer Wiring
| Contact No. | Function | Cross-sectional area | Core Wire Color |
| 1 | Left-hand direction indicator light | 1.5mm2 | Yellow |
| 2 | Right-hand direction indicator light | 1.5mm2 | Green |
| 3 | Rear fog light | 1.5mm2 | Blue |
| 4 | Common return | 2.5mm2 | White |
| 5 | Left-hand rear position and marker lights, and license plate lamp | 1.5mm2 | Black |
| 6 | Right-hand rear, position and marker lights, and license plate lamp | 1.5mm2 | Brown |
| 7 | Brake light | 1.5mm2 | Red |
| 8 | Reversing light | 1.5mm2 | Pink |
| 9 | Continuous power supply (steady constant) | 2.5mm2 | Orange |
| 10 | Worn brake line sensor | 1.5mm2 | Grey |
| 11 | Pressure sensor for spring brake | 1.5mm2 | White/black |
| 12 | Axle lifting device | 1.5mm2 | White/blue |
| 13 | Common return for data lines | 2.5mm2 | White/red |
| 14 | CAN-H | 1.5mm2 | White/green |
| 15 | CAN-L | 1.5mm2 | White/brown |
Cable Type Recommend
- Cable Sheath: PVC or PUR (Preferred)
- Cable Size: 3x 2.5mm2 + 12x 1.5mm2
Connectors Recommend
- Plug: ISO12098 Reinforced Composite Plug (with Spring parts is preferred)
- Socket: ISO12098 Reinforced Composite Socket
IV Conclusion
KMCABLE has over 15 years of experience in supplying trailer electrical connection solutions. Our trailer coil can be found any where like Dongfeng Volvo Scania. If you have any needs for trailer Coils, straight cable, wiring harnesses, or plugs. Welcome to inquire with us. We will be a good supplier if you want.
