Mercedes-Benz CLS550 Turn Signal Bulb Size

Additional Notes

• The Mercedes-Benz CLS550 front turn signal uses one of two bulb types across its model years: the 3457NA or the 3357NA, both of which are ANSI-standardized T25 wedge bulbs rated for 12V operation and designed for the North American market.
• The 3457NA is a dual-filament bulb rated at 27W and 7W, meaning it carries two independent circuits within a single housing, allowing it to serve both a primary and a secondary lighting function simultaneously.
• The 3357NA is a single-filament bulb rated at 27W, carrying only one active circuit and therefore suited exclusively for a single lighting function such as a dedicated turn signal.
• Both bulb types feature natural amber glass, which produces the amber turn signal color directly from the bulb itself rather than relying on a colored lens housing.
• The CLS550 (2010-2011) uses the 3457NA dual-filament bulb for the front turn signal position.
• The 2009-2008 model years use the 3357NA single-filament bulb in the same front turn signal position.
• The 2007 model year returns to the 3457NA dual-filament specification, making it distinct from the two immediately following years.
• Although the 3457NA and 3357NA share the same T25 wedge base and physical housing format, substituting one for the other is not straightforward, as the filament count differs and an incorrect substitution may result in non-functional circuits or improper behavior.