The Mercedes-Benz SL320 front turn signal requires a 2357NA bulb in P21/5W size, while the rear turn signal uses a P21W bulb size. The replacement chart covers 1994 to 1997 production years with corresponding bulb specifications.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Mercedes-Benz SL320 front turn signal specification changed between model years, with 1994-1995 using the P21/5W bulb and 1996-1997 using the 2357NA bulb.
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, housed in natural amber glass with a BAY15d bayonet base.
The P21/5W is an ECE-standard dual-filament bulb rated at 12V with filaments drawing 21W and 5W respectively, also fitted with a BAY15d bayonet base.
Although both the 2357NA and P21/5W share the BAY15d bayonet base, they are not interchangeable due to differing wattage ratings and regulatory standards, with the 2357NA following ANSI specifications and the P21/5W following ECE specifications.
The natural amber glass of the 2357NA produces its amber signal color through the bulb itself, whereas housing or lens color may serve that function in applications using clear-glass ECE bulbs.
The rear turn signal on the SL320 used the P21W across all four model years from 1994-1997, indicating no change in that position over the documented period.
The P21W is a single-filament ECE-standard bulb rated at 12V and 21W, fitted with a BA15s bayonet base, which is a single-contact base distinct from the dual-contact BAY15d base used on the front turn signal bulbs.
Because the rear P21W uses a BA15s base and the front bulbs use a BAY15d base, the front and rear turn signal bulbs for the SL320 are physically non-interchangeable regardless of model year.