Mercury Mountaineer front and rear turn signal bulbs utilize 3157NA size for front applications, with rear positions accommodating 3157NA, 3057, or 2356 bulb sizes. The replacement chart covers 1997 through 2010 model 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 Mercury Mountaineer uses the 3157NA bulb for the front turn signal across all model years covered in the specifications, spanning 1997-2010.
The 3157NA is a dual-filament T25 wedge bulb rated at 12V with a 27W high-filament and 7W low-filament draw, and it features natural amber glass, which produces an amber color output without the need for an amber lens or housing.
The rear turn signal of the Mercury Mountaineer uses the 3157NA for 2006-2010, meaning the front and rear positions share the same bulb type during those years.
For the 2003-2005 Mountaineer, the rear turn signal takes a 3057 bulb instead. The 3057 is also a dual-filament T25 wedge bulb rated at 12V, 27W/7W, but it lacks the natural amber glass coating of the 3157NA.
Although the 3057 and 3157NA share the same T25 wedge base and wattage ratings, their optical output differs due to the amber glass on the 3157NA. Substituting one for the other may affect the color output at the lens.
The 2001 Mountaineer rear turn signal uses a 2356 bulb, which is a dual-filament bulb with a BAY15d bayonet base rather than a wedge base, making it physically incompatible with sockets designed for T25 wedge bulbs.
The 1997-2000 Mountaineer rear turn signal uses a 2456 bulb, which is a festoon-type bulb intended for specialty applications, representing a distinct socket type from both the wedge and bayonet formats used in other model years.
The rear turn signal position of the Mountaineer uses four different bulb types across the full 1997-2010 model year range, and direct substitution between them is not supported by the specifications due to differing base types and constructions.
All bulb types listed in the specifications conform to ANSI standards applicable in both the United States and Canada, and all operate on a 12V electrical system.
The 3157NA is the most frequently specified bulb across both front and rear positions in the Mountaineer turn signal data, appearing in all 14 front turn signal entries and in 5 of the 14 rear turn signal entries.