The Mercedes-Benz 240D front turn signal requires either a P21/5W or P21W bulb size, while the rear turn signal uses a P21W bulb size. The replacement chart covers vehicle production spanning 1974 to 1983 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 P21W and P21/5W bulb types are the two bulb sizes specified across all front and rear turn signal positions on the Mercedes-Benz 240D for model years 1974-1983.
Both bulb types conform to ECE standards, meaning they are recognized across European and worldwide automotive lighting regulations.
The P21W is a single-filament bulb rated at 12V and 21W, fitted with a BA15s bayonet base. The single-filament design means it serves one lighting function only.
The P21/5W is a dual-filament bulb rated at 12V with filaments at 21W and 5W, fitted with a BAY15d bayonet base. The dual-filament design allows it to serve two distinct lighting functions within a single housing.
The BA15s base on the P21W and the BAY15d base on the P21/5W are not interchangeable. The BAY15d base uses offset pins to prevent incorrect installation, while the BA15s base uses aligned pins.
The front turn signal on the Mercedes-Benz 240D uses the P21/5W for model years 1977-1983 and the P21W for model years 1974-1976, representing a difference in bulb type across the production run.
The rear turn signal position uses the P21W across all listed model years, 1974-1983, without variation.
Because the front turn signal shifted from P21W to P21/5W at the 1977 model year, a P21W bulb is not a direct substitute for the front position on 1977-1983 models, as the base type and filament configuration differ.