Pontiac Executive Back Up Light Bulb Size

The Pontiac Executive back up light requires bulb size 1157, 1156, or P21W depending on the specific version of the component. Data for the bulb sizes covers the range from 1967 to 1970.

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
1969-1970	1157
1967-1968	1156

Bulb Specifications

Description	Bulb Size
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. 12V, 21W.	1156

Other Locations

Additional Notes

The Pontiac Executive uses two distinct bulb types across its model years for the back up light position: the 1156 for 1967-1968 and the 1157 for 1969-1970.
Both the 1156 and 1157 are ANSI standardized bulbs recognized in the United States and Canada, operating on a 12-volt electrical system.
The 1156 is a single-filament bulb rated at 21W, mounted on a BA15s bayonet base, which features a single locating pin on the base collar.
The 1157 is a dual-filament bulb rated at 21W and 5W, mounted on a BAY15d bayonet base, which features two offset locating pins to prevent incorrect installation.
Although the 1156 and 1157 share a similar physical profile and both use 15mm bayonet bases, they are not interchangeable due to the difference in base pin configuration between BA15s and BAY15d.
The shift from the 1156 to the 1157 between the 1968 and 1969 Pontiac Executive represents a change from a single-filament to a dual-filament bulb in the back up light circuit.
The secondary 5W filament in the 1157 is a characteristic of bulbs designed for dual-function lamp housings, where one filament serves a separate lighting role alongside the primary function.