The Mercedes-Benz SLK230 front turn signal bulb utilizes 3457NA, 2357NA, or P21/5W size, while the rear turn signal bulb uses 1156NA size. The replacement chart covers 1998 to 2004 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 2357NA bulb is the most frequently specified front turn signal bulb for the Mercedes-Benz SLK230, covering model years 1998-1999 and 2001-2003. It is a dual-filament bulb with a BAY15d bayonet base, rated at 12V with a power draw of 26.9W on the high filament and 8W on the low filament.
The 1156NA bulb is the sole rear turn signal specification across all listed model years, 1998-2004. It is a single-filament bulb with a BA15s bayonet base, rated at 12V and 21W, with natural amber glass.
Both the 2357NA and 1156NA carry the "NA" suffix, which denotes natural amber glass. This coloring is built into the glass envelope itself rather than relying on an amber-tinted lens in the vehicle's housing.
The 2357NA and 1156NA share a similar bayonet-style mounting family, but they are not interchangeable. The 2357NA uses a BAY15d base, which has two offset pins to accommodate its dual-filament design, while the 1156NA uses a BA15s base with a single pin suited to its single-filament construction.
The 2004 model year front turn signal uses the 3457NA rather than the 2357NA found in prior years. The 3457NA is also a dual-filament bulb with natural amber glass, rated at 12V and 27W/7W, but it uses a T25 wedge base rather than a bayonet base, making it physically incompatible with sockets designed for the 2357NA.
The year 2000 front turn signal position lists two separate bulbs: a P21/5W designated as the main bulb and a 12961 designated as the side marker. This two-bulb arrangement for a single position is distinct from all other listed model years, which each specify only one front turn signal bulb.
The P21/5W is governed by the ECE standard used in Europe and worldwide markets, whereas all other bulbs in these specifications follow the ANSI standard used in the US and Canada. The P21/5W shares the BAY15d bayonet base with the 2357NA, but its wattage ratings of 21W/5W differ, and the two standards are not directly interchangeable without confirming socket and housing compatibility.
The 12961 is a Philips part number for a miniature T10 wedge bulb with a W2.1x9.5d base, rated at 12V and 5W. Its low wattage reflects its role as a side marker rather than a primary signaling source.
The dual-filament bulbs in these specifications, the 2357NA, 3457NA, and P21/5W, each serve two lighting functions from a single socket. In a turn signal application, the higher-wattage filament typically handles the flashing signal function while the lower-wattage filament serves a secondary role such as a parking or position light.
The rear turn signal circuit for the SLK230 uses a single-filament bulb across all listed years, which is consistent with a dedicated turn signal housing where no secondary lighting function is required from the same socket.