Different installation processes are required depending on which light bulb needs to be replaced in a vehicle. To replace the headlight bulb, locate the holder, and remove the power wires. Remove the old bulb, and then clean and install the new one. To replace the tail light bulb, locate and unscrew the housing, and then pull out or unscrew the bulb, replacing it with the new one.
Access the headlight bulb through the vehicle's engine compartment by opening the hood and locating the headlight. Locate and remove the power wires, which are usually attached to a plug at the bottom of the light. Remove the old bulb while holding onto the base of the headlight, and install the new one in its place. Return the holder back to its original position, and plug the wires back in.
Replacing tail lights requires a different process. After locating the housing, unscrew it along with any other screws or knobs necessary, pull out or unscrew the bulb, and replace it with the new one.
When replacing a signal light bulb, the location varies depending on the age and make of the vehicle. With older vehicles, the signal lights are separate from the headlights, whereas newer vehicles combine assembly of the headlights and signal lights. After locating the bulb, pull it out or unscrew it, and replace it with the clean, new one.