GMC Brigadier Back Up Light Bulb Size

The GMC Brigadier back up light uses 1156 and 1073 bulb sizes depending on the specific application for the vehicle. Data for the bulb sizes covers the range from 1984 to 1988.

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
1988	1156 (Tiltmaster)
1986-1987	1073 (Tiltmaster)
1985	1156 (Tiltmaster)
1984	1073 (Tiltmaster)

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 GMC Brigadier (Tiltmaster) back up light specifications cover model years 1984-1988, with two distinct bulb types appearing across those years: the 1156 and the 1073.
Both the 1156 and 1073 are ANSI-standard bulbs recognized in the US and Canada, and both share the BA15s single-contact bayonet base configuration.
The BA15s base is a single-contact bayonet mount, meaning the bulb seats and locks with a push-and-twist motion against one electrical contact at the base tip.
Both bulb types operate at 12 volts, consistent with standard automotive electrical systems.
The 1156 is rated at 21 watts, while the 1073 is rated at 13 watts, making the 1073 a lower-output variant despite sharing the same base type as the 1156.
Because the 1156 and 1073 share the BA15s base, one may physically fit the socket of the other, but their wattage ratings differ significantly, which affects light output and circuit load.
The 1985 and 1988 Brigadier Tiltmaster models use the 1156 bulb, while the 1984, 1986, and 1987 models use the 1073 bulb.
Both bulbs are single-filament types, which is typical for back up lights, as that function requires only one consistent illumination state with no high or low setting.