Chevrolet Chevelle Back Up Light Bulb Size

The Chevrolet Chevelle back up light uses 1156 and P21W bulb sizes according to the provided data. Information for the lighting components covers the range from 1964 to 1973.

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
1964-1973	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 Chevrolet Chevelle uses the 1156 bulb for its back up light across all listed model years, spanning 1964-1973.
The 1156 is a single-filament bulb, meaning it serves one lighting function only, which in this application is the back up light.
It operates on a 12-volt electrical system and draws 21 watts, placing it in the standard incandescent output range for reverse lighting of that era.
The 1156 uses a BA15s bayonet base, where "BA15s" denotes a single-contact bayonet fitting with a 15mm base width. This base type requires a twist-and-lock installation rather than a screw-in mount.
The "s" in BA15s indicates a single contact point at the base, distinguishing it from the dual-contact BA15d base found on two-filament bulbs such as the 1157. These two bulb types are not interchangeable despite sharing the same base width.
The 1156 carries an ANSI designation, confirming it meets standardized specifications recognized across the United States and Canada.