The Mark 4 Jetta and Golf are very popular with auto enthusiasts because they are easily modifiable. Volkswagen uses modular designs to allow easy parts swaps from one model to another or to allow easy compliance with local laws. One popular parts change for VW owners is to remove headlight assemblies designed for the American market and replace them with the European versions.
Because of the way that the regulations are written, automobile manufacturers have more leeway in how a European headlight looks. At the same time, they have less leeway in how a European light illuminates the road.
Some American drivers prefer the way the European light makes the front end of the car look, while other appreciate the lighting pattern. In either case, the European versions are only legal for off-road use in the United States.
European market cars are required to have a city light function, which American cars are not required to have. To add this function to the MK4 or Mk5 Jetta or Golf, you can replace the American headlight switch with a European version. This switch will also allow the fog lights to be used without the headlights. The "Euro Switch" is installed without tools and is widely available online. When installing European market headlights, you need this switch.
The low beam lighting pattern is very different from one side of the Atlantic to the other. In the U.S., headlamps are required to put some light up to illuminate overhead signs. European lights may not cast light up in order to combat light pollution. American lights cast light both to the left and right of the vehicle, while European lights have a sharp reduction in light on the left to cut down glare for oncoming drivers. Because the European pattern is designed to cut down glare, brighter lamps are acceptable in Europe, and European lights cast light further down the road.
As stated earlier, European market headlight assemblies do not meet US DOT regulations. The European version puts out too much light. Depending on the style chosen, the lens cover of the European version may be tinted, which is illegal in the US. The European lights will not cast enough light up or to the left to be legal.
