High Intensity Discharge (HID) Headlamps
WARNING: This page is about a different car, the 2011 Mercury Milan, 2011 Lincoln MKZ, and 2011 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.