[TrevorS]

Hello, I'm new, I got myself a 2008 scion xb, I got a hid kit from vvme. They were good in my previous car.

My question is, do you need a relay kit in order for the hids to function correctly?

I did a plug nd play and the hid turned on fine, what's the function of the relay?

The purpose of the relay is to protect the OE headlight wiring from the additional power drawn by the HID ballasts. A ballast can require 75W continuous whereas the OE low beam Halogen draws 55W. Still, the same gauge wiring also powers the 60W Halogen high beams, so given the probable current overdraw is modest, plug and play probably isn't that risky.