Mercury Sable Back Up Light Bulb Size

The Mercury Sable back up light utilizes bulb sizes 921, 2356, 3156, 2456, and P21W depending on the specific version. Data for the components covers the range from 1986 through 2009.

The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.

Bulb Size by Year Range

Years	Bulb Size
2008-2009	921
1999	2356
1998	3156
1997	2456
1996	2356
1986	P21W

Bulb Specifications

Description	Bulb Size
ANSI standard (US & Canada). Wedge bulb (T15). 12V, 16W.	921
ANSI standard (US & Canada). Dual-filament bulb with BAY15d bayonet base. 12V.	2356
ANSI standard (US & Canada). Single-filament wedge bulb (T25). 12V, 27W.	3156
ANSI standard (US & Canada). Festoon bulb, specialty application. 12V.	2456
ECE standard (Europe & worldwide). Single-filament signalling bulb with BA15s bayonet base. 12V, 21W.	P21W

Other Locations

Additional Notes

The Mercury Sable backup light specifications reference five distinct bulb types across the model's production years: 921, 2356, 3156, 2456, and P21W.
The 921 is a T15 wedge bulb rated at 12V and 16W, conforming to the ANSI standard used in the United States and Canada. It is specified for the 2008-2009 Mercury Sable.
The 3156 is a single-filament T25 wedge bulb rated at 12V and 27W, also under the ANSI standard. Its wattage is notably higher than the 921, reflecting a greater light output for the backup function in the 1998 model year.
The 2356 is a dual-filament bulb with a BAY15d bayonet base, rated at 12V under the ANSI standard. A dual-filament design means the bulb contains two separate filaments, each serving a different lighting function, which distinguishes it from the single-filament types also present in these specifications.
The 2456 is a festoon-style bulb rated at 12V under the ANSI standard, noted as a specialty application. A festoon bulb is cylindrical in shape and contacts at both flat ends rather than through a base, making it physically incompatible with wedge or bayonet sockets.
The P21W follows the ECE standard rather than the ANSI standard, placing it in a regulatory category used in Europe and internationally. It is a single-filament bulb with a BA15s bayonet base, rated at 12V and 21W, and is specified for the 1986 model year.
The BA15s base of the P21W and the BAY15d base of the 2356 are both bayonet-style fittings, but they are not interchangeable. The BA15s is a single-contact base, while the BAY15d has two contacts offset at different heights to prevent incorrect installation.
The wedge-base bulbs (921 and 3156) and the bayonet-base bulbs (2356 and P21W) require different socket types, meaning substitution across these base categories is not physically possible without socket modification.
The ANSI-standard bulbs (921, 2356, 3156, and 2456) share the same nominal operating voltage of 12V, consistent with standard automotive electrical systems in North America.
The shift from the ECE-standard P21W in 1986 to ANSI-standard bulbs in subsequent years reflects a change in the bulb specification framework applied to the Mercury Sable across its production history.