American Motors AMX Back Up Light Bulb Size

The American Motors AMX back up light uses bulb sizes 1156 and P21W according to the provided specifications for the lighting components. Data for the lighting assemblies covers the range from 1968 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
1978-1980	1156
1968-1970	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 1156 is the sole bulb type listed across all model years of the American Motors AMX for the back up light position.
The 1156 operates on a 12-volt electrical system and draws 21 watts, which is typical of single-filament incandescent bulbs used in directional or reverse lighting applications.
A single filament means the 1156 serves one lighting function only, distinguishing it from dual-filament bulbs such as the 1157, which handle two functions within a single housing.
The BA15s bayonet base uses a single locating pin on the side of the base, and this pin placement is not interchangeable with the BA15d base, which carries two offset pins.
The 1156 conforms to ANSI standards recognized in both the United States and Canada, indicating a standardized specification rather than a proprietary or regional variant.
The AMX used the 1156 across the 1968-1970 model years as well as the 1978-1980 model years, reflecting consistent back up light socket design across those respective production periods.