The Mercedes-Benz 280E front turn signal requires a P21/5W bulb size while the rear turn signal uses a P21W bulb size. The replacement chart covers 1977 through 1981 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 280E requires two distinct bulb types across its turn signal positions for the 1977-1981 model years: P21/5W at the front and P21W at the rear.
The P21/5W is a dual-filament bulb rated at 12V with a 21W primary filament and a 5W secondary filament, mounted on a BAY15d bayonet base.
The BAY15d base features two offset pins at different heights, a design that physically prevents incorrect filament orientation during installation.
The P21W is a single-filament bulb rated at 12V and 21W, mounted on a BA15s bayonet base, which uses a single contact pin rather than the dual-pin arrangement of the BAY15d.
Because the P21/5W and P21W use different base types, BAY15d and BA15s respectively, the front and rear bulbs are not interchangeable with each other.
Both bulb types conform to ECE standards, a regulatory framework recognized across Europe and numerous other markets worldwide.
The dual-filament configuration of the P21/5W at the front position indicates that a single bulb serves more than one lighting function in that location.
The P21W at the rear position operates as a dedicated single-function signalling bulb, with its full 21W output directed to one filament.