The Mercedes-Benz 250 front and rear turn signal bulbs both utilize a P21W size. The replacement chart covers 1968 to 1973 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 P21W is the sole bulb type specified for the Mercedes-Benz 250, covering both the front and rear turn signal positions across the 1968-1973 model years.
The P21W is a single-filament bulb, meaning it serves one lighting function only, which is consistent with its dedicated use in turn signal applications rather than combined stop/tail positions.
The P21W operates at 12 volts and 21 watts, placing it in the standard range for automotive signalling bulbs where higher wattage relative to parking or side marker bulbs produces the brightness required for turn signal visibility.
The P21W uses a BA15s bayonet base, where "BA" denotes a bayonet cap fitting, "15" refers to a 15mm base width, and the lowercase "s" indicates a single contact at the base, corresponding to its single-filament design.
The P21W is governed by ECE (Economic Commission for Europe) standards and is used across European and worldwide markets, reflecting the regulatory environment under which the Mercedes-Benz 250 was engineered.
Because the front and rear turn signal positions on the Mercedes-Benz 250 share the same P21W specification across all listed years, the bulb is interchangeable between those two positions on the vehicle.
The BA15s base of the P21W is not interchangeable with the BA15d base, which carries two offset contact pins at the base for dual-filament bulbs. Substituting a BA15d bulb in a BA15s socket is not compatible.