The Volkswagen Passat has been sold around the world since 1973, although it wasn't always called the Passat in America. The American Passat had an identity crisis; it was first called the Fox, then the Dasher and Quantam, until it was finally branded with the Passat name in 1990 (and every year since). Replacing the headlights in a Passat is a little more involved than some vehicles, because of the lack of space in the engine bay.
Pull off the plastic air intake cover, remove the intake mounting bolt and set the intake hose aside (passenger side only).
Twist off the protective rubber cover from the back of the headlight assembly. Press the tab to pull off the electrical connector.
Turn the bulb socket counter clockwise to unlatch it, and then slip it away from the assembly.
Turn the old bulb counterclockwise to release it from the socket. Install the new bulb by turning it clockwise. Hold the plastic base of the new bulb when installing it. Touching the glass can cause it to prematurely fail.
Insert the module and turn it clockwise to lock it into the assembly. Reattach the electrical connector and twist the protective rubber cover onto the back of the assembly.
Reattach the intake hose (passenger side only) and tighten the bolt. Snap the plastic intake cover back on.
This procedure is applicable to all models of the Volkswagen Passat, 2001.5 to 2009. Installation will be similar for older models, but they may require a different type of bulb.
If your Passat is equipped with HID Xenon headlights, bring it to a dealer for replacement.