Chevrolet Bel Air Back Up Light Bulb Size

The Chevrolet Bel Air back up light utilizes 1156, 1073, and P21W bulb sizes depending on the specific production period for the vehicle. Available data for the lighting components spans from 1955 through 1975.

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
1958-1975	1156
1955-1957	1073

Bulb Specifications

Description	Bulb Size
ANSI standard (US & Canada). Single-filament bulb with BA15s bayonet base. 12V, 21W.	1156
ANSI standard (US & Canada). Single-filament bulb with BA15s bayonet base. Lower wattage variant of 1156. 12V, 13W.	1073

Other Locations

Additional Notes

The Chevrolet Bel Air uses two bulb types across its back up light specifications: the 1156 and the 1073, both of which are ANSI-standardized for the US and Canadian markets.
Both the 1156 and 1073 are single-filament bulbs sharing the BA15s bayonet base and a 12-volt operating voltage, which places them in the same base family despite differing in wattage.
The 1156 operates at 21 watts, while the 1073 operates at 13 watts, making the 1073 a lower-wattage variant within the same base category.
Although the 1156 and 1073 share the BA15s bayonet base, their wattage difference means they are not interchangeable without accounting for the change in light output, as the 1156 produces noticeably more illumination than the 1073.
The Chevrolet Bel Air (1958-1975) specifies the 1156 bulb for its back up lights across that entire span of model years.
The 1073 bulb is specified for the 1955-1957 model years, representing the earlier wattage standard used in back up lighting for that period.
The transition from the 1073 to the 1156 occurred between the 1957 and 1958 model years, reflecting a shift to the higher-wattage 21W specification.