Buick LaCrosse Turn Signal Bulb Size

Additional Notes

• The 3757NA bulb is the most frequently specified type across the Buick LaCrosse turn signal positions, covering both front and rear applications across the 2010-2013 model years. It is a dual-filament T25 wedge bulb rated at 12V with natural amber glass, conforming to ANSI standards for the US and Canadian markets.
• Natural amber glass, denoted by the "NA" suffix in bulb designations such as 3757NA, 7443NA, 4157NA, and 7440NA, produces an amber-colored output directly from the glass envelope rather than relying on a clear bulb behind an amber lens. The 2017-2018 rear turn signal position specifies the 7440, which lacks this amber glass coating.
• The front turn signal position on the 2005-2009 LaCrosse uses the 4157NA, a dual-filament T25 wedge bulb rated at 12V with a 27W/7W output. This differs from the 3757NA that replaced it in the 2010-2013 model years for the same position.
• The 7443NA, specified for the front turn signal on the 2014-2016 LaCrosse, is a dual-filament T20 wedge bulb rated at 12V with a 21W/5W output. Although it shares the T20 form factor with the 7440 and 7440NA, its dual-filament construction distinguishes it from those single-filament types.
• The rear turn signal on the 2005-2009 LaCrosse uses the 3057, a dual-filament T25 wedge bulb rated at 12V with a 27W/7W output. Unlike the 3757NA that follows it in later years, the 3057 does not carry the natural amber glass designation.
• The front left and front right turn signal positions are listed separately for the 2010-2013 LaCrosse and both specify the 3757NA exclusively for vehicles equipped with High Intensity Discharge headlights. The 2011 front right turn signal row does not carry this HID qualifier, while all other left and right entries for those years do.
• T25 and T20 designations refer to the outer envelope width of the wedge bulb, with T25 indicating a wider profile than T20. The LaCrosse specifications include both sizes across different positions and model years, meaning T25 and T20 bulbs are not interchangeable despite sharing a wedge base style.
• The rear turn signal transitions from a single-filament 7440NA in 2014-2016 to a 7440 in 2017-2018. Both are T20 wedge bulbs rated at 12V and 21W, with the sole difference being the presence of natural amber glass on the 7440NA and its absence on the 7440.
• Dual-filament bulbs such as the 3757NA, 7443NA, 4157NA, and 3057 serve two circuit functions within a single housing, commonly combining turn signal and parking light duties. Single-filament types such as the 7440 and 7440NA serve only one circuit function.
• All six bulb types specified across the LaCrosse turn signal positions conform to ANSI standards applicable to both the United States and Canada, operating on a 12V electrical system consistent with standard automotive applications.