Buick Century Back Up Light Bulb Size

The Buick Century back up light uses 1156, P21W, and 1073 bulb sizes depending on the specific production period. Available information covers the range from 1954 to 2005.

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
1997-2005	1156
1973-1985	1156
1954-1958	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 Buick Century backup light specifications cover two distinct bulb types across its model years: the 1156 and the 1073.
Both the 1156 and 1073 are ANSI-standardized bulbs recognized in the US and Canada, each using a BA15s single-contact bayonet base.
The BA15s base is a single-contact bayonet mount, meaning the bulb seats and locks with a push-and-twist motion and carries current through one contact point at the base.
Both bulb types are single-filament designs, which is typical for backup lights since the function requires only one consistent output state rather than variable brightness levels.
The 1156 operates at 12V and 21W, while the 1073 operates at 12V and 13W, making wattage the primary electrical distinction between the two types.
The Buick Century (1973-2005) uses the 1156 bulb for its backup lights, with the exception of the 1997-1999 and 2000-2005 model years, all of which share the same specification.
The Buick Century (1954-1958) uses the 1073 bulb for its backup lights.
Although the 1156 and 1073 share the same BA15s bayonet base, they are not interchangeable without consequence, as the wattage difference of 8W means the 1073 draws significantly less current than the 1156.
Substituting a 1073 in a socket specified for a 1156 would result in a dimmer output, since the lower wattage produces less luminous intensity.
The shared base type between the 1156 and 1073 means a physical fit is possible in either socket, making wattage verification an important step before installation.