What is the blue wire for on my trailer plug?
What is the blue wire for on my trailer plug – trailer wiring.
The blue wire on a trailer is typically used for the electric brake system. It connects to the electric brakes on the trailer, allowing the vehicle to control the braking system when the tow vehicle applies the brakes.
In general, trailer wiring can follow different colour codes depending on the manufacturer, but the blue wire is commonly associated with service brakes in most wiring configurations.
Here’s a quick overview of common trailer wire colours and their functions:
- Brown: Rear Lamps, Side Marker lamps
- Yellow: Left turn signal and brake light
- Green: Right turn signal and brake light
- White: Ground
- Blue: Electric brakes (or sometimes auxiliary power).
On a European trailer the blue wire represents the fog light.
The other new wire is the grey or pink wire.
- This presents the reverse light.
- Reverse: When wiring a European wired trailer to an Australian vehicle, the grey /pink wire goes to auxiliary and as such will work for the reverse light.
- Fog: The fog light system in Australia has yet to be decided upon in
regard to wiring. However, the ideal position to connect the blue wire would be the service brakes (no 5). In turn, your vehicle should be wired to match. This is only suitable if you will be using a mechanical braked trailer, as the electric brakes (service brakes) vehicle wiring will be disconnected.
European trailer wired 7 pin plug – Australia only.
7 Pin Flat Trailer Plug and Socket Wiring Diagram
With 12 pins, the fog lamp wire (blue) would be connected to Pin 11. However, a standard trailer will only require a 7-pin plug.
With the other trailer plug wires – there is also a difference. A European or UK trailer uses individual wiring for the park/clearance lights (Left side and right side) Brown and black.
The brown and black wires should both be connected in the plug to pin no. 7 –
The reverse lamp is a grey wire. This should be connected to pin no. 2.
Australian wired 12 pin plug the blue (Fog lamp) is connected to pin 11.
A fog lamp has a higher rated lumen and it is recommended not to attach to the stop lamps (pin 6).
Australian wired 7 pin plug
Australian wired 12 pin plug –
