Pontiac Catalina Back Up Light Bulb Size

The Pontiac Catalina back up light utilizes 1129, 1073, 1157, 1156, and P21W bulb sizes depending on the specific version of the vehicle. Available data for the components spans from 1950 through 1981.

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
1974-1981	1156
1973	1157
1971-1972	1156
1969-1970	1157
1958-1968	1156
1955-1957	1073
1950-1954	1129

Bulb Specifications

Description	Bulb Size
ANSI standard (US & Canada). Single-filament bulb with BA15s bayonet base. 12V, 21W.	1156
ANSI standard (US & Canada). Dual-filament bulb with BAY15d bayonet base. 12V, 21W/5W.	1157
ANSI standard (US & Canada). Single-filament bulb with BA15s bayonet base. Lower wattage variant of 1156. 12V, 13W.	1073
ANSI standard (US & Canada). Dual-filament bulb with BAY15d bayonet base. Variant of 1157. 12V, 21/5W.	1129

Other Locations

Additional Notes

The Pontiac Catalina back up light bulb specifications span model years 1950 through 1981, covering four distinct bulb types across that range.
The 1156 is the most frequently specified bulb across the Catalina lineup, appearing in model years 1958-1968, 1971-1972, and 1974-1981. It is a single-filament, 12V, 21W bulb with a BA15s bayonet base, conforming to ANSI standards for the US and Canada.
The 1157 bulb is specified for the 1969-1970 and 1973 Catalina. Unlike the 1156, it carries a dual-filament design rated at 12V with a 21W primary filament and a 5W secondary filament, mounted on a BAY15d bayonet base.
The BAY15d base of the 1157 is physically offset from the BA15s base of the 1156, meaning the two bulb types are not interchangeable despite sharing a similar appearance and voltage rating.
The 1073 bulb is specified for the 1955-1957 Catalina. It shares the same BA15s bayonet base as the 1156 but operates at a lower wattage of 13W rather than 21W, making it a lower-output variant of that bulb type.
Because the 1073 and 1156 share the BA15s base, physical fitment between the two is possible, though their wattage ratings differ and substitution may not meet original electrical specifications.
The 1129 bulb is specified for the 1950-1954 Catalina. It is a dual-filament bulb rated at 12V, 21W/5W, using a BAY15d bayonet base, and is classified as a variant of the 1157.
The 1129 and 1157 share the same BAY15d base type, which means the two are physically compatible in terms of socket fitment, though they remain distinct ANSI part numbers.
All four bulb types across the Catalina specifications conform to ANSI standards applicable in both the United States and Canada.
The transition from dual-filament 1129 bulbs in the early 1950s to single-filament 1073 bulbs in 1955 represents a shift in back up light configuration for the Catalina at that point in its production history.