High Intensity Discharge (HID) Headlamps
WARNING: This page is about a different car, the 2010 Mercury Milan, 2010 Lincoln MKZ, and 2010 Ford Fusion. However, it is still accessible from the selected car via links, so may be relevant.
Each HID headlamp consists of a ballast and replaceable low and high beam bulbs. The ballasts provide the higher voltage required for the HID bulbs to illuminate.
When the low beams are on, the HID ballasts provide high voltage to the HID bulbs.