GMC 150 Dome Light Bulb Size

The GMC 150 dome light requires a 1156 or 94 bulb size for proper illumination. The replacement chart covers 1956 through 1959 production years with corresponding bulb specifications.

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
1958-1959	1156
1956-1957	94

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. Variant of 1157. 12V, 21/5W.	94

Other Locations

Additional Notes

The GMC 150 dome light uses two distinct bulb types across its 1956-1959 model years: the 1156 for 1958-1959 and the 94 for 1956-1957.
Both the 1156 and 94 bulbs follow ANSI standards applicable in the US and Canada, operating at 12 volts.
The 1156 is a single-filament bulb rated at 21W, fitted with a BA15s bayonet base, which has a single locating pin on its base collar.
The 94 is a dual-filament bulb rated at 21/5W, fitted with a BAY15d bayonet base, which has two offset locating pins to prevent incorrect insertion.
Because the BA15s and BAY15d bases differ in pin configuration, the 1156 and 94 bulbs are not interchangeable despite sharing the same 12V operating voltage and a common 21W filament rating.
The 94 bulb is a variant of the 1157, sharing its dual-filament design and BAY15d base, though the two are not necessarily identical in all electrical ratings.