Oct 30, 2014 · * If you wire pin 3 from a switched 12V source, the AUX lights will only work when the ignition switch is in the "ON" position. * Additionally, you can wire pin 3 from any 12V supply wire on the vehicle, but be aware that the AUX lights will only operate when that specific supply wire is active. Pin 4 is the output to the relay. Nice!. On mine (2018) the fog light relay is the one next to your finger on the right and the relay is negative switched, so I wired it to the negative of the headlight relay. When headlights are switched on, headlight relay coil is grounded and the fog light relay coil will be grounded too thus turning on the fog lights.