Pontiac Grand Safari Back Up Light Bulb Size

The Pontiac Grand Safari back up light utilizes 1156, 1157, and P21W bulb sizes depending on the specific version required for the vehicle. Data for the bulb sizes covers the range from 1971 through 1978.

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
1974-1978	1156
1973	1157
1971-1972	1156

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

Other Locations

Additional Notes

The Pontiac Grand Safari back up light specifications cover model years 1971 through 1978.
The 1156 bulb is the dominant fitment across this generation of the Grand Safari, appearing in seven of the eight model years listed, specifically 1971-1972 and 1974-1978.
The 1156 is a single-filament bulb operating at 12 volts with a 21-watt output, mounted on a BA15s bayonet base, and recognized under ANSI standards in both the United States and Canada.
The BA15s bayonet base features a single contact pin, which physically distinguishes it from multi-pin bayonet bases used on other bulb types.
The 1973 Grand Safari departs from the surrounding model years by specifying the 1157 bulb for the back up light position.
The 1157 is a dual-filament bulb rated at 12 volts, with filaments drawing 21 watts and 5 watts respectively, and it seats into a BAY15d bayonet base.
The BAY15d base uses two offset pins rather than the single pin of the BA15s, making the 1156 and 1157 physically non-interchangeable despite sharing the same voltage rating.
Although both bulbs share the same 21-watt primary filament output, the 1157 carries an additional 5-watt filament that the single-filament 1156 does not possess, which further distinguishes their electrical behavior.
Substituting a 1156 in place of a 1157, or vice versa, is not possible without a socket adapter due to the differing base configurations.