The Mercedes-Benz 380SEL uses a P21/5W bulb size for the front turn signal and a P21W bulb size for the rear turn signal. The replacement chart covers vehicle production spanning 1981 to 1983.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Mercedes-Benz 380SEL uses two distinct bulb types across its turn signal positions: the P21/5W at the front and the P21W at the rear, both conforming to ECE standards recognized across Europe and worldwide.
Both bulb types operate on a 12-volt electrical system, which is standard for automotive applications of this era.
The P21/5W is a dual-filament bulb rated at 21W and 5W, with the lower-wattage filament typically serving a secondary function such as a parking or position light alongside the primary turn signal filament.
The P21W is a single-filament bulb rated at 21W, dedicated solely to turn signal operation at the rear of the vehicle.
The front turn signal position on the 380SEL uses a BAY15d bayonet base, which is an offset twin-pin fitting designed specifically for dual-filament bulbs to prevent incorrect installation.
The rear turn signal position uses a BA15s bayonet base, a single-pin fitting suited to single-filament applications.
The BAY15d and BA15s bases are physically incompatible with each other, meaning the front and rear bulbs are not interchangeable despite sharing the same 21W primary wattage rating.
The front P21/5W and rear P21W specifications remained consistent across the 1981-1983 model years of the 380SEL.