Mercury Mariner front inner turn signal bulbs use 3457NA or 3357NA size, front turn signal bulbs use 3457NA or 3157NA size, and rear turn signal bulbs use 4157 or 3157 size. The replacement chart covers 2005 through 2011 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 Mercury Mariner turn signal specifications reference five distinct bulb types across its front and rear positions: 3457NA, 3357NA, 3157NA, 4157, and 3157.
Four of these five bulb types, specifically the 3457NA, 3157NA, 4157, and 3157, share identical electrical ratings of 12V with a dual-filament output of 27W/7W, making them functionally equivalent in power draw despite their different part numbers.
The 3357NA is the only single-filament bulb among the five types listed, rated at 12V and 27W, which distinguishes it electrically from the dual-filament bulbs used elsewhere in the same vehicle.
All five bulb types conform to the T25 wedge form factor and are classified under the ANSI standard applicable to both the United States and Canada.
The "NA" suffix on the 3457NA, 3357NA, and 3157NA designations indicates natural amber glass, meaning the amber color is built into the glass envelope rather than achieved through a clear bulb in an amber-tinted housing.
The 3457NA is the most frequently specified bulb across the Mercury Mariner's turn signal positions, appearing in the front inner turn signal for 2005-2007 and 2009-2011, and in the front turn signal for 2006-2011.
The 2008 front inner turn signal position on the Mercury Mariner specifies a 3357NA rather than the 3457NA used in all other model years for that position, a notable fitment difference given that the 3357NA is single-filament while the 3457NA is dual-filament.
The front turn signal for the 2005 Mercury Mariner uses a 3157NA, while all subsequent model years through 2011 use a 3457NA for that same position.
The rear turn signal transitions from the 3157 bulb used in 2005-2006 to the 4157 bulb used in 2007-2011. Both share the same T25 wedge base and 12V/27W/7W ratings, though they carry different ANSI part numbers.
Because the 3357NA is a single-filament bulb and the 3457NA is a dual-filament bulb, the two types are not interchangeable despite sharing the same T25 form factor and voltage rating.