Mercury Bobcat Back Up Light Bulb Size

The Mercury Bobcat back up light uses 1156 and P21W bulb sizes for the rear illumination system. Data for the specified vehicle components covers the period from 1975 through 1980.

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
1975-1980	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 Bobcat uses the 1156 bulb for the back up light across the 1975-1980 model years.
The 1156 is an ANSI-standardized bulb, meaning its specifications are governed by a recognized North American standard shared across the United States and Canada.
The 1156 operates on a 12-volt electrical system and draws 21 watts, which is typical for incandescent back up light applications.
The 1156 is a single-filament bulb, meaning it serves one lighting function only, as opposed to dual-filament bulbs that handle two functions such as braking and running lights simultaneously.
The 1156 uses a BA15s bayonet base, where "BA15s" denotes a bayonet fitting with a 15mm base width and a single contact pin, which locks the bulb into the socket with a push-and-twist motion.
The consistent use of the 1156 across all six model years of the Mercury Bobcat indicates no mid-generation change to the back up light socket or housing design during that period.
The BA15s single-contact base of the 1156 is not interchangeable with the BA15d base found on dual-filament bulbs, as the pin configuration differs between the two base types.