The Mercedes-Benz 500SEL uses 1034 and P21/5W bulbs for front turn signals, along with P21W bulbs for rear turn signals, with each size corresponding to specific lighting positions. The replacement chart covers 1984 to 1993 production years and details bulb size specifications across the vehicle's model run.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Mercedes-Benz 500SEL uses three distinct bulb types across its front and rear turn signal positions: the 1034, the P21/5W, and the P21W.
The 1034 and P21/5W are both dual-filament bulbs rated at 12V with a 21W main filament and a 5W secondary filament, and both use a BAY15d bayonet base, making them physically interchangeable in terms of base fitment.
Despite sharing the same BAY15d base and wattage ratings, the 1034 follows the ANSI standard used in the United States and Canada, while the P21/5W follows the ECE standard used in Europe and worldwide, reflecting a regional specification difference in the 500SEL's front turn signal fitment.
The 1034 is a variant of the widely used 1157 bulb type, which is one of the most common dual-filament automotive bulbs in North American applications.
The front turn signal on the 500SEL uses the 1034 for the 1992-1993 model years and the P21/5W for the 1984-1985 model years, indicating a shift in regional bulb standard between these production periods.
The rear turn signal uses the P21W across all four model years covered in the specifications, from 1984-1985 and 1992-1993, making it the most consistently applied bulb type in this dataset.
The P21W is a single-filament bulb rated at 12V and 21W, using a BA15s bayonet base. Its single-filament design and BA15s base distinguish it from the dual-filament P21/5W, which uses the BAY15d base, and the two are not interchangeable despite similar naming.
The BAY15d base used by both the 1034 and P21/5W features offset pins to prevent incorrect installation, a design characteristic that differentiates it from the single-pin BA15s base used by the P21W.
Because the front and rear turn signals on the 500SEL use different base types in all listed model years, bulbs for these two positions cannot be substituted for one another regardless of wattage similarity.
The P21/5W designation follows ECE naming conventions in which the first wattage figure refers to the main filament and the second to the secondary filament, a format that differs from the numerical ANSI codes such as 1034 used in North American standards.