The Mercedes-Benz 420SEL uses 9004 bulb size for both high beam and low beam headlight applications. The replacement chart covers vehicle production years spanning 1986 to 1991.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Mercedes-Benz 420SEL uses the 9004 bulb type for both high beam and low beam headlights across all model years from 1986-1991.
The 9004 is a dual-filament halogen bulb, meaning a single bulb unit contains two separate filaments to serve both the high beam and low beam functions within one housing.
Because the 9004 handles both beam functions in the 420SEL, the high beam and low beam positions share the same bulb specification rather than requiring separate bulb types for each role.
The 9004 operates on a 12-volt electrical system and carries wattage ratings of 65W for the high beam filament and 45W for the low beam filament.
The 9004 bulb uses a P29t base, which is a specific connector and socket configuration. Bulbs with a different base type are not physically compatible with this socket, regardless of voltage or wattage similarity.
The 9004 is an ANSI-standardized bulb type recognized in the United States and Canada, meaning its electrical and physical specifications conform to a defined industry standard rather than a proprietary format.