Mercedes-Benz S550 high beam headlight bulbs use H9 and H7 sizes, while low beam headlight bulbs use D1S size. The replacement chart covers 2007 to 2013 model years with corresponding bulb size specifications.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The D1S bulb is the low beam specification for the Mercedes-Benz S550 across all seven model years listed, from 2007-2013. It is a high-intensity discharge (HID) xenon bulb rated at 85V and 35W, which places it in a fundamentally different technology category from the halogen bulbs used in the high beam position.
The D1S bulb features a PK32d-2 base with an integral ignitor built directly into the bulb body. This design means the ignitor is not a separate component housed in the vehicle, and the bulb is intended specifically for projector-type headlight housings rather than reflector-style assemblies.
The high beam position on the S550 uses two different halogen bulb types depending on the model year. The H7 bulb was specified for 2007-2010, while the H9 replaced it for 2011-2013. These two bulbs are not interchangeable, as they use different base types: the H7 uses a PX26d base and the H9 uses a PGJ19-5 base.
The H7 and H9 are both single-filament halogen bulbs operating at 12V, but they differ in wattage. The H7 is rated at 55W, while the H9 is rated at 65W, making the H9 a higher-output bulb by 10 watts.
Both the H7 and H9 bulbs carry ECE certification, which is the regulatory standard used across Europe and much of the world. Both are also approved for use in the United States, and the H7 additionally holds approval in Japan.
The high beam transition from H7 to H9 occurred between the 2010 and 2011 model years of the S550. Because the two bulbs use physically distinct base configurations, a bulb from the 2010 specification cannot be substituted into a 2011-2013 housing, and vice versa.
The D1S operates at 85 volts, which is substantially higher than the 12-volt supply used by the halogen high beam bulbs. This voltage difference reflects the arc-discharge operating principle of HID technology, which requires a high-voltage ignition pulse to initiate and sustain a plasma arc between two electrodes rather than heating a tungsten filament.
Despite its higher operating voltage, the D1S draws only 35W during steady-state operation, which is lower than both the 55W H7 and the 65W H9. This reflects the greater luminous efficiency of HID discharge technology relative to halogen filament technology at equivalent or lower power consumption.