Chevrolet Biscayne Back Up Light Bulb Size

The Chevrolet Biscayne back up light utilizes 1156, P21W, and 1073 bulb sizes depending on the specific production requirements for the vehicle. Provided data covers the range from 1958 through 1972 for the listed components.

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
1963-1972	1156
1962	1073
1959-1961	1156
1958	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 backup light bulb for the Chevrolet Biscayne is specified as the 1156 across the majority of model years covered, spanning 1959-1972 with the exception of 1958 and 1962.
The 1156 is an ANSI-standard single-filament bulb rated at 12 volts and 21 watts, fitted with a BA15s bayonet base, which is a single-contact base with a 15mm collar.
The 1073 bulb is specified for the 1958 and 1962 Biscayne. It is also an ANSI-standard single-filament bulb with a BA15s bayonet base, but operates at a lower wattage of 13 watts at 12 volts.
Because both the 1156 and 1073 share the BA15s bayonet base, they are physically interchangeable in terms of socket fitment, but their wattage ratings differ and each is specified for distinct model years.
The lower wattage of the 1073 relative to the 1156 means the two bulbs produce different light output levels, which is a relevant factor when considering substitution between the two types.
The single-filament construction of both bulb types indicates they serve a dedicated switching function, consistent with their application as backup lights rather than dual-purpose stop or tail light bulbs.