Mercedes-Benz C350 Turn Signal Bulb Size

Additional Notes

• The PY24WNA is the most frequently specified front turn signal bulb for the Mercedes-Benz C350, covering the 2011-2015 model years when equipped with halogen capsule headlamps. It operates at 12V and 24W, uses a PGU20-4 base, and is the amber ANSI-market variant of the ECE-standard PY24W.
• The NA suffix present on PY24WNA, 3457NA, 3357NA, 1156NA, and 2357NA designates natural amber glass, meaning the bulb produces an amber signal output without relying on a colored lens or housing to filter a clear light source.
• All front turn signal bulbs specified for the C350 conform to ANSI standards, making them designated for the US and Canadian markets, while the PY21W rear turn signal bulb follows ECE standards used in Europe and worldwide markets.
• The 2007 and 2006 model years carry two distinct front turn signal specifications depending on headlamp type. Vehicles with halogen capsule headlamps use the 1156NA, a single-filament BA15s bayonet bulb rated at 21W, while vehicles with HID headlamps use the 2357NA, a dual-filament BAY15d bayonet bulb rated at 26.9W/8W.
• The 1156NA and 2357NA share a similar physical form factor but use different bayonet bases. The 1156NA has a BA15s single-contact base, while the 2357NA has a BAY15d offset dual-contact base. These bases are not interchangeable, and substituting one for the other is not possible without modification.
• The 3457NA, specified for the 2010 and 2008 front turn signal positions, is a dual-filament T25 wedge bulb rated at 27W/7W. The 3357NA, specified for 2009, is a single-filament T25 wedge bulb rated at 27W. Although both share the T25 form factor and natural amber glass, their filament counts differ, and they are not functionally interchangeable in circuits designed for dual-filament operation.
• The PY21W rear turn signal bulb, specified for the 2006, 2008, and 2011 model years, uses a BAU15s bayonet base. This base features an offset pin arrangement that physically prevents installation of standard BA15s or BAY15d bulbs, serving as a keying mechanism to ensure correct bulb fitment.
• The 12496 is a Philips and Osram part number rather than an ANSI or ECE standard designation. It is rated at 12V and is classified as a specialty halogen application bulb. It appears in the rear turn signal position for the 2007, 2009, and 2010 model years.
• The rear turn signal specifications for the C350 alternate between the PY21W and the 12496 across model years, indicating that different rear lamp assemblies were used during the production run, and these two bulb types are not cross-compatible due to differing base configurations and standards.
• The PY24WNA operates at 24W, which is notably higher than the 21W output of the PY21W and 1156NA. This wattage difference is relevant when assessing load compatibility with electronic turn signal flasher circuits, which may be calibrated to a specific wattage range to regulate flash frequency.