GMC PM251 Dome Light Bulb Size

The GMC PM251 dome light requires a unique 94 bulb size for proper installation and function within the interior cabin. Data for the specific bulb requirements covers the range from 1956 to 1957.

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
1956-1957	94

Bulb Specifications

Description	Bulb Size
ANSI standard (US & Canada). Dual-filament bulb with BAY15d bayonet base. Variant of 1157. 12V, 21/5W.	94

Other Locations

Additional Notes

The GMC PM251 uses the 94 bulb for its dome light across the 1956-1957 model years.
The 94 bulb follows the ANSI standard, meaning it conforms to specifications recognized across the United States and Canada.
This bulb type features a dual-filament design, which allows it to operate at two distinct wattage levels within a single unit.
The 94 uses a BAY15d bayonet base, a two-pin offset base that physically prevents incorrect insertion by positioning its pins at different heights.
The 94 is a variant of the 1157 bulb, indicating a close relationship in design and electrical characteristics between the two types.
Operating voltage is rated at 12V, consistent with the standard electrical systems found in automotive applications of that era.
The dual-filament configuration draws either 21W or 5W depending on which filament is active.