The Mercedes-Benz C320 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 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 1156NA is the most frequently specified front turn signal bulb across the Mercedes-Benz C320 range, appearing in 2001-2005 model years under halogen capsule headlamp configurations. It is a single-filament bulb with a BA15s bayonet base, natural amber glass, rated at 12V and 21W, and follows the ANSI standard used in the United States and Canada.
The 2357NA bulb is specified for the Mercedes-Benz C320 front turn signal in 2003-2005 model years, but only in vehicles equipped with HID headlamps. Unlike the 1156NA, it is a dual-filament bulb with a BAY15d bayonet base, rated at 12V with a 26.9W high filament and 8W low filament.
The BA15s base of the 1156NA and the BAY15d base of the 2357NA are physically incompatible. The BAY15d base has offset pins to prevent incorrect installation, meaning the two bulbs are not interchangeable despite sharing the same natural amber glass and 12V operating voltage.
Front turn signal bulb selection on the C320 for 2003-2005 is determined by headlamp type. Halogen capsule headlamp trims use the 1156NA, while HID headlamp trims use the 2357NA. The 2001-2002 model years list only the 1156NA with no headlamp-type distinction.
The rear turn signal of the Mercedes-Benz C320 uses two distinct bulb types across its production run. The PY21W is specified for 2001 and 2004-2005, while the 12496 is specified for 2002-2003, indicating a mid-cycle change and a later reversion.
The PY21W follows the ECE standard used in Europe and worldwide markets. It is a single-filament amber bulb with a BAU15s bayonet base, rated at 12V and 21W. The BAU15s base uses asymmetric pin placement, distinguishing it from the BA15s base of the 1156NA, and the two are not interchangeable.
The 12496 is a Philips/Osram part number designation rather than an ANSI or ECE standard code. It is classified as a halogen bulb for specialty applications, rated at 12V, and is specified for the C320 rear turn signal in 2002-2003.
Although the 1156NA and PY21W share the same wattage rating of 21W and single-filament construction, their base types differ. The 1156NA uses a BA15s base with symmetric pins, while the PY21W uses a BAU15s base with offset pins, making them physically non-interchangeable.