Mercedes-Benz 600SEL front side marker bulbs use 1034 size while rear side marker bulbs use P21/4W size. The replacement chart covers 1992 to 1993 vehicle production years with corresponding bulb specifications.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Mercedes-Benz 600SEL uses two distinct bulb standards across its side marker positions: the ANSI-standard 1034 at the front and the ECE-standard P21/4W at the rear, covering the 1992-1993 model years for both positions.
The 1034 bulb follows ANSI standards applicable in the United States and Canada, while the P21/4W follows ECE standards used in Europe and worldwide, reflecting a split between regional lighting regulations within the same vehicle.
Both the 1034 and P21/4W are dual-filament bulbs operating at 12 volts, which is consistent with standard automotive electrical systems.
The 1034 bulb carries a 21/5W power rating, meaning its two filaments draw 21 watts and 5 watts respectively depending on the active circuit.
The P21/4W bulb carries a 21W/4W power rating, a configuration typical of signalling applications where one filament serves a brighter function and the other a dimmer one.
The 1034 uses a BAY15d bayonet base, which features two offset pins at different heights to ensure correct polarity orientation during installation.
The P21/4W uses a BAZ15d bayonet base, which also has two pins but with a different offset geometry than the BAY15d, making the two bulbs physically non-interchangeable despite their similar dual-filament design.
The BAY15d and BAZ15d bases are not cross-compatible, so the front and rear side marker bulbs of the 600SEL cannot be substituted for one another even though both operate at 12V with dual filaments.
The 1034 is described as a variant of the 1157, a widely used ANSI bulb, though the 1034 designation indicates a specific variant rather than a direct equivalent.