Cadillac Eldorado Back Up Light Bulb Size

The Cadillac Eldorado back up light utilizes unique bulb sizes 2057, 3057, 1156, P21W, and 1073 depending on the specific production version. Available data covers the range from 1953 through 2002.

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
1992-2002	2057
1990-1991	3057
1958-1989	1156
1953-1957	1073

Bulb Specifications

Description	Bulb Size
ANSI standard (US & Canada). Dual-filament bulb with BAY15d bayonet base. Brighter variant of 1157. 12V, 26.9W/8W.	2057
ANSI standard (US & Canada). Dual-filament wedge bulb (T25). 12V, 27W/7W.	3057
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 Cadillac Eldorado back up light specifications span model years 1953 through 2002, covering three distinct bulb types across that range: the 1073, 1156, and 2057, with the 3057 appearing in a brief transitional period.
The 1156 bulb is the most frequently specified type in these records, covering the Cadillac Eldorado from 1958 through 1989. It is a single-filament bulb with a BA15s bayonet base, rated at 12V and 21W.
The 2057 bulb is specified for the 1992-2002 Cadillac Eldorado. It is a dual-filament bulb with a BAY15d bayonet base, rated at 12V with filament wattages of 26.9W and 8W, and is noted as a brighter variant of the 1157.
The BAY15d base of the 2057 and the BA15s base of the 1156 are physically distinct. Despite a similar outward profile, these two base types are not interchangeable, as the BAY15d has offset pins to prevent incorrect installation of a dual-filament bulb in a single-filament socket.
The 3057 is specified for the 1990-1991 Cadillac Eldorado. It is a dual-filament bulge-style T25 wedge bulb rated at 12V with filament wattages of 27W and 7W, and it does not use a bayonet base.
The 1073 bulb is specified for the 1953-1957 Cadillac Eldorado. It shares the BA15s bayonet base with the 1156 but operates at a lower wattage of 13W at 12V, making it a lower-output variant of that bulb family.
Because the 1073 and 1156 share the same BA15s base type, physical fitment between the two is possible, though their wattage ratings differ. The 1073 is rated at 13W while the 1156 is rated at 21W, which reflects a meaningful difference in light output for a back up light application.
All four bulb types in these specifications conform to ANSI standards applicable in both the United States and Canada, indicating standardized dimensional and electrical tolerances across the range.
The transition from the single-filament 1156 to the dual-filament 3057 between the 1989 and 1990 model years represents a socket and wiring compatibility change, as a single-filament socket cannot fully utilize a dual-filament bulb.
The subsequent change from the 3057 wedge-base bulb to the 2057 bayonet-base bulb between the 1991 and 1992 model years represents another base-type change, meaning the socket design in the lamp housing also changed between those model years.