The Mercedes-Benz C240 front turn signal requires 1156NA or 2357NA bulb sizes, while the rear turn signal uses PY21W or 12496 bulb sizes. The replacement chart covers 2001 to 2005 production 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 1156NA is a single-filament bulb rated at 12V and 21W, built to the ANSI standard used in the United States and Canada. It uses a BA15s bayonet base and features natural amber glass rather than a clear envelope with an amber-coated housing.
The 2357NA shares the same ANSI standard and natural amber glass construction as the 1156NA but differs in two significant ways: it carries a dual-filament design and uses a BAY15d bayonet base, which has offset pins to prevent incorrect installation. Its wattage is rated at 26.9W on the high filament and 8W on the low filament.
The PY21W follows the ECE standard used in Europe and worldwide rather than the ANSI standard. It uses a BAU15s bayonet base, which has asymmetrically offset pins, making it physically incompatible with the BA15s and BAY15d bases found on the 1156NA and 2357NA.
On the Mercedes-Benz C240, the front turn signal position requires different bulb sizes depending on headlamp type. Vehicles equipped with halogen capsule headlamps use the 1156NA, while those equipped with HID headlamps use the 2357NA. This distinction applies to the 2003-2005 model years.
The 2001 and 2002 model years list only the 1156NA for the front turn signal, with no headlamp-type variants specified, indicating a single fitment for those years.
The BA15s base of the 1156NA and the BAY15d base of the 2357NA are physically distinct. Substituting one for the other is not possible without a base adapter, as the pin configurations differ between single-contact and dual-contact bayonet designs.
The rear turn signal position on the C240 shifted from the 12496 to the PY21W between the 2002 and 2003 model years. The 12496 is a Philips/Osram part number designation for a 12V halogen bulb used in specialty applications, while the PY21W is an internationally standardized ECE type.
The PY21W rear turn signal bulb appears on the 2004-2005 model years, while the 12496 covers the 2001-2003 model years. Because the PY21W uses a BAU15s base and the 12496 is a specialty halogen type, the two are not interchangeable without confirming base compatibility.