Headlight Bulb
The replaceable electrical lamp element inside a vehicle's headlight assembly that provides forward illumination.
A headlight bulb is the replaceable light source inside a vehicle's forward headlight housing. There are three main types of headlight bulbs in use: halogen bulbs (which use a tungsten filament inside a capsule of halogen gas), High-Intensity Discharge (HID/Xenon) bulbs (which create light via an electrical arc between electrodes), and LED bulbs (which use semiconductor chips to produce light with high efficiency).
Replacing a burned-out headlight bulb is a basic maintenance task critical for night-driving safety and legal compliance. When installing new halogen or HID bulbs, it is critical never to touch the glass capsule with bare fingers. The oils from your skin can create hot spots on the quartz glass, causing the bulb to shatter or fail prematurely when it heats up.
If a bulb is replaced but still fails to light, the issue may lie with a blown fuse, a bad relay, or corroded wiring contacts in the bulb connector. Adjusting the aim of the headlight housing after bulb replacement ensures correct road illumination without blinding oncoming drivers.