High intensity discharge (HID) headlights are xenon gas bulbs that last longer, use less energy and produce three times more usable light than halogens. They work in conjunction with a ballast that regulates the electricity flow. HID lights are part of a package including fog lights for the Toyota Prius. When HID lights go out or when HID replacement bulbs aren't available, you may want to convert from HID lights back to halogen bulbs as an interim measure.
Disconnect the HID ballast. The ballast is a small box with a regulating power supply that delivers consistent electricity so that the high intensity beam does not fluctuate. It is integral to an HID assembly and is not necessary to power halogen bulbs.
Remove the HID headlamps from the headlight housing by twisting the light assembly counterclockwise slightly. Removal of the fuse box cover offers more room to access the driver's side headlight.
Connect the halogen headlamp wires directly to the power source wire connector/harness by unplugging the HID ballast wires from the power source wire connector.
Install the halogen bulbs into the light assembly after removing the HID bulbs.
Lock the new bulb assembly in place by twisting it clockwise then turn the car lights on to test them.
