American Motors Gremlin Back Up Light Bulb Size

The American Motors Gremlin back up light uses 1156 and P21W bulb sizes for the rear illumination system. Data for the specified components covers the period from 1970 through 1978.

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
1970-1978	1156

Bulb Specifications

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

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Additional Notes

The 1156 is the sole back up light bulb size listed across all model years of the American Motors Gremlin covered by these specifications, spanning 1970-1978.
The 1156 is an ANSI-standardized bulb type, meaning its physical and electrical characteristics conform to a defined North American standard recognized in both the United States and Canada.
It operates on a 12-volt electrical system and draws 21 watts, which is typical for incandescent automotive reverse lighting applications.
The 1156 uses a BA15s bayonet base, a single-contact fitting where the "s" denotes a single pin rather than the offset dual-pin arrangement found on related bayonet types such as the BA15d.
As a single-filament bulb, the 1156 performs one lighting function only, distinguishing it from dual-filament variants like the 1157, which serve multiple functions such as combined stop and tail lighting.
The BA15s base type is not interchangeable with dual-contact bayonet bases. Substituting a dual-filament bulb with a BA15d base into a BA15s socket is not possible without modification, as the pin configuration differs.