Wiring Tips for Electric Brakes


These instructions are a guide only and assume some basic working knowledge of electrical systems. It also assumes tow vehicle has been wired to a standard 7 pin configuration. Not all vehicles are wired to Australian Standards or wired the same. If you do not have the required test tools (or the ability to use them) to find fault problems should they arise, please refer the job to a qualified auto electrician.

It is recommended that at least a 12 gauge (2.5sqmm) 2 core wire is used and run alongside the standard 24 gauge (0.64sqmm) 5 core wire, which is used for lighting applications on trailers. Heavier wire ensures voltage drops do not occur in the system.


1. One wire from the 2 core flex (typically red) needs to be connected to the trailer electrical plug pin 5 (auxiliary brake).

2. The other wire (typically black) needs to be connected to trailer electrical plug pin 3 (earth). Earthing faults are generally the most common problem that will occur, so a good earth back to the tow vehicle's earth system is important.

3. The 2 core wire is then run alongside the 5 core lighting cct wire along (or inside) the drawbar and inside or underneath the body to the braked axle. Allow enough wire for suspension movement when dropping wire from frame to axle.

4. Connect braked wire (red) to one of the wires protruding from the electric brake assembly. (The magnets can be wired either way so it doesn't matter which one)

5. At this connection point, run another wire directly across the axle to one of the wires protruding from the electric brake assembly on the other side of the trailer and connect. The power to brake magnets is now complete.

6. Repeat Steps (4) and (5) for earth (black wire). The earth to brake magnets is now complete. (Wiring for 4 wheel electric brakes follows the same method). It is recommended that the wiring should be run along rear of braked axle, preferably in some sort of protective shroud (e.g. garden hose). This protects against damage to wiring from road debris.

7. To test brakes, connect trailer to tow vehicle fitted with an electric brake controller. Apply brakes and an audible 'click' should be heard when listening to the braked hubdrum, followed by a constant 'buzz' until the brakes are released. This indicates brake magnets are working.

When towing, set gain on electric controller as per manufacturers directions according to loads being towed, e.g. Heavier loads require higher gain for heavier application of brakes.

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