The Mercedes-Benz CLK500 front turn signal uses a P21W, 1156NA, or 2357NA bulb size, while the rear turn signal requires either a PY21W or P21W bulb size. The replacement chart covers 2003 to 2006 model years 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 Mercedes-Benz CLK500 front turn signal uses different bulb sizes depending on the model year and headlamp type, with three distinct bulb specifications appearing across the 2003-2006 range.
The 1156NA is an ANSI-standard single-filament bulb rated at 12V and 21W, fitted with a BA15s bayonet base and natural amber glass. It is specified for the front turn signal on 2003-2005 CLK500 models equipped with halogen capsule headlamps.
The 2357NA is an ANSI-standard dual-filament bulb rated at 12V with a high filament draw of 26.9W and a low filament draw of 8W, fitted with a BAY15d offset-pin bayonet base and natural amber glass. It is specified for the front turn signal on 2004-2005 models equipped with HID headlamps.
The BAY15d base on the 2357NA has two offset pins, which physically prevents it from being interchanged with the BA15s base used on the 1156NA, despite both bulbs sharing the same 12V rating and amber glass coating.
The 2003 CLK500 with HID headlamps uses the 1157NA for the front turn signal rather than the 2357NA specified for 2004-2005 HID-equipped models. The 1157NA is also a dual-filament BAY15d bulb but is rated at 21W/5W, making it a lower-wattage specification than the 2357NA.
The 2006 CLK500 front turn signal uses the P21W, an ECE-standard single-filament bulb rated at 12V and 21W with a BA15s bayonet base. Unlike the 1156NA, the P21W uses a clear glass envelope rather than natural amber glass.
The rear turn signal on the 2003-2005 CLK500 uses the P21W across all three years. The 2006 model shifts to the PY21W for the rear position.
The PY21W is an ECE-standard single-filament bulb rated at 12V and 21W, but it uses a BAU15s base with a single offset pin. This offset distinguishes it from the BA15s base of the P21W, and the two are not interchangeable despite sharing the same wattage and voltage rating.
The "NA" suffix on ANSI bulb designations such as 1156NA, 2357NA, and 1157NA indicates natural amber glass, which produces the amber signal color without requiring an amber lens. The equivalent clear-glass versions of these bulbs would not meet turn signal color requirements in the same housings.
The front turn signal specifications for the CLK500 reflect a distinction between halogen capsule and HID headlamp configurations in 2003-2005, indicating that the headlamp type on these vehicles is a relevant factor in determining the correct front turn signal bulb.