The Mercedes-Benz E430 tail light requires a specific 12821 bulb size for proper installation and function. Data for the specified component covers the period from 1998 through 2002.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The P21/4W is an ECE-standard dual-filament bulb rated at 12V with a 21W main filament and a 4W secondary filament, mounted on a BAZ15d bayonet base. The asymmetric wattage between filaments allows a single bulb to serve two distinct lighting functions simultaneously.
The BAZ15d base on the P21/4W uses an offset pin configuration, which physically prevents incorrect installation. This is a deliberate safety feature in dual-filament bulbs, ensuring the higher-wattage filament is always connected to the correct circuit.
The Mercedes-Benz E430 outer tail light uses the P21/4W for the primary position across model years 1998-2002, with the sole exception of 1999, which lists bulb size 12961 instead.
Both 12961 and 12821 are Philips part numbers for T10 miniature wedge bulbs sharing identical electrical ratings of 12V and 5W, and both use the W2.1x9.5d base. Despite these shared characteristics, they carry distinct part numbers and are not listed interchangeably within these specifications.
The T10 wedge bulb format, used by both the 12961 and 12821, relies on the wedge-shaped glass envelope itself to make contact within the socket, with no separate base pins or bayonet lugs involved in retention.
The 12821 appears consistently across all five model years (1998-2002) in the outer tail light specifications, making it the most uniformly applied bulb size across the entire E430 model range covered here.
The 1999 model year is the only year in these specifications where the outer tail light lists 12961 rather than P21/4W for the primary position, while still retaining the 12821 for the secondary position shared with all other years.