The Mercedes-Benz 300SE front side marker bulb uses a 1034 or P21/5W size, while the rear side marker bulb requires a P21/4W or 3893 size. The replacement chart covers 1988 to 1993 production 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 Mercedes-Benz 300SE uses dual-filament bulbs across all listed front and rear side marker positions for the 1988-1993 model years.
The front side marker position of the 300SE uses two distinct bulb types depending on the model year: the P21/5W for 1988-1991 and the 1034 for 1992-1993.
The P21/5W is an ECE-standard signalling bulb rated at 12V with a 21W main filament and a 5W secondary filament, mounted on a BAY15d bayonet base.
The 1034 is an ANSI-standard bulb rated at 12V with a 21W/5W dual-filament configuration, also using a BAY15d bayonet base, and is classified as a variant of the 1157.
Because both the P21/5W and the 1034 share the BAY15d bayonet base and carry identical voltage and wattage ratings, they are physically and electrically similar, though they originate from different standardization systems (ECE and ANSI respectively).
The rear side marker position of the 300SE also splits across two bulb types: the 3893 for 1988-1991 and the P21/4W for 1992-1993.
The P21/4W is an ECE-standard bulb rated at 12V with a 21W main filament and a 4W secondary filament, but it uses a BAZ15d bayonet base rather than the BAY15d base found on the P21/5W and 1034.
The BAZ15d base of the P21/4W features offset pins in a different configuration than the BAY15d, which means P21/4W bulbs are not interchangeable with P21/5W or 1034 bulbs despite their similar appearance.
The 3893 is an ANSI-standard dual-filament bulb with a BAY15d bayonet base, designated for specialty applications and rated at 12V.
The front and rear side marker positions on the 300SE do not share a common bulb type in any listed model year, requiring separate bulb selections for each position.