The Mercedes-Benz 500SL uses a P21/5W bulb size for the front turn signal and a 1156 bulb size for the rear turn signal. The replacement chart covers vehicle production spanning 1990 to 1993.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Mercedes-Benz 500SL uses two different bulb standards across its front and rear turn signal positions for the 1990-1993 model years.
The front turn signal on the 500SL takes the P21/5W bulb, an ECE-standard type used across European and worldwide markets. It operates at 12V and carries a dual-filament design rated at 21W and 5W, mounted on a BAY15d bayonet base.
The dual-filament construction of the P21/5W means the bulb serves more than one lighting function from a single housing, with the 21W filament typically handling the turn signal and the 5W filament serving a secondary role such as a position or parking light.
The rear turn signal takes the 1156 bulb, an ANSI-standard type common to the US and Canadian markets. It is a single-filament bulb rated at 12V and 21W, seated in a BA15s bayonet base.
Although both the P21/5W and the 1156 share a bayonet-style base and operate at 12V with a 21W primary filament, they are not interchangeable. The P21/5W uses a BAY15d base with offset pins to accommodate its dual-filament design, while the 1156 uses a BA15s base with a single contact point.
Attempting to substitute a single-filament 1156 into a front turn signal socket designed for the dual-filament P21/5W would result in an incorrect fit due to the differing base configurations.
The front and rear turn signal positions on the 500SL therefore require separate bulb types, and the two are not cross-compatible despite their shared voltage rating and similar wattage on the primary filament.