Relay Harnesses

A wire harness is necessary to adapt your factory harness to work with your newly retrofitted HID headlights. Generally speaking you can't just plug the ballasts into where the halogen bulbs went before and expect them to work reliably or even at all. A harness works this way: Your factory socket that originally connected to the halogen bulb now switches on a relay. The relay is a switch that draws power from the car battery and sends it out to the ballasts. It's pretty simple, but this tends to be the part that confuses and deters people from doing a retrofit. In the end, the harness will allow the HID retrofit (Bi-xenon or low beam only) to operate just like stock. Read more about Wire Harnesses at TRS Tech.