Mercury Capri Back Up Light Bulb Size

The Mercury Capri back up light utilizes 1156 and P21W bulb sizes according to the provided technical data. Available information covers the span from 1970 through 1994.

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
1991-1994	1156
1979-1986	1156
1970-1977	1156

Bulb Specifications

Description	Bulb Size
ANSI standard (US & Canada). Single-filament bulb with BA15s bayonet base. 12V, 21W.	1156

Other Locations

Additional Notes

The Mercury Capri uses the 1156 bulb for the back up light position across all model years covered in the specifications, from 1970 to 1994.
The 1156 is a single-filament bulb, meaning it serves one lighting function only, which is consistent with its application in a dedicated back up light position.
The 1156 operates at 12 volts and 21 watts, placing it in the standard range for incandescent automotive signal and utility lighting.
The bulb uses a BA15s bayonet base, a single-contact bayonet mount where the "s" denotes a single pin, as opposed to the dual-pin BA15d variant.
The 1156 carries ANSI standardization recognized in both the United States and Canada, indicating a consistent specification across North American markets.
Because the BA15s base is a single-contact design, it is not interchangeable with physically similar bulbs that use a BA15d dual-contact base, even though the outer housing size may appear comparable.
The 1156 is sometimes confused with the 1157, which shares a similar bayonet base style but is a dual-filament bulb with a BA15d base, making the two types incompatible in the Mercury Capri's back up light socket.