Wiring up the relay harness for your LED lights may seem complicated with all of the long wires and connecting that you have to do, but when you lay out all of the components and understand how the wiring diagram works, then the process becomes infinitely easier. A relay harness provides power directly from the vehicle’s battery and provides a more consistent power source for the lighting. This guide will show you how to wire up your relay harness so you can install some LED fog lights or any other LED lighting application.
There are two components to the entire relay harness: the side with the actual relay and the side with the on/off switch. Once you remove the zip-tie holding the wires together, you will notice that the wires are pretty long so you will need to sort of untangle and tidy them up. To give you an idea of the wiring length, this relay harness has been tested on a Ford F-250 without any issue with length. These wires are even designed to be heavy duty and can withstand up to 180W.
We will now start from the side with the relay.
Route the relay through the engine bay and connect the wires to the LED fog lights or any other lighting application such as LED daytime running lights or LED work lights.
For the relay side:
Connect the positive wire to battery positive and negative wire to the ground.
Connect the single white wire to the switch.
Connect the remaining wires to your fog lamps. The shorter wires are to be on the side where the battery is located. The longer wires will need to be routed to the side of the vehicle that does not have the battery.
For the switch side:
The white wire should already be connected to the relay.
Connect the black wire to ground and the red wire to ACC 12V+.
Run the switch from inside of the car through the firewall and up to the engine bay.
Once you connect all the wires properly, you will see the red LED indicator on the switch light up. This means that the wiring is successful and ready to go. Press the button on the switch. The light will turn green and your LED fog lamps will light up.
If you’re wondering if the wires are long enough, the relay harness has been tested on a Ford F-250 without any issue with length. These wires are even designed to be heavy duty and can withstand up to 180W. Enjoy your new LED fog lights.