Ford F-250 Engine Compartment Light Bulb Size

The Ford F-250 engine compartment light utilizes bulb sizes 912, 90, 105, and 631 depending on the specific production period for the vehicle. Available data for the components spans the range from 1969 through 1999.

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
1992-1999	912
1988-1991	90
1985-1986	90
1975-1979	105
1969-1974	631

Bulb Specifications

Description	Bulb Size
ANSI standard (US & Canada). Wedge bulb (T15). Variant of 921. 12V, 12W.	912
ANSI standard (US & Canada). Single-filament bulb with BA15s bayonet base. 12V, 13W.	90
ANSI standard (US & Canada). Single-filament bulb with BA15s bayonet base. Variant of 1156. 12V, 13W.	105
ANSI standard (US & Canada). Single-filament bulb with BA15s bayonet base. Variant of 1156. 12V, 21W.	631

Other Locations

Additional Notes

The Ford F-250 engine compartment light uses four distinct bulb sizes across its model history: 912, 90, 105, and 631, each representing a different era of the vehicle's production.
The 912 bulb, fitted to the 1992-1999 Ford F-250, is a T15 wedge-type bulb rated at 12V and 12W, and it is classified as a variant of the 921 under the ANSI standard.
Wedge-type bulbs such as the 912 use a plastic base with wire contacts rather than a metal bayonet fitting, which makes them physically incompatible with sockets designed for bayonet-base bulbs.
The 90 bulb, used in the 1985-1991 F-250 (excluding 1987), carries a BA15s single-contact bayonet base and is rated at 12V and 13W.
The 105 bulb, specified for the 1975-1979 F-250, shares the same BA15s bayonet base and 12V, 13W rating as the 90, and is classified as a variant of the 1156 under the ANSI standard.
Although the 90 and 105 bulbs share the same base type and electrical ratings, they are distinct ANSI part numbers and are not listed as interchangeable within these specifications.
The 631 bulb, fitted to the 1969-1974 F-250, also uses a BA15s bayonet base but is rated at a notably higher 21W output compared to the 90 and 105 bulbs, despite sharing the same base configuration.
The 631 is also classified as a variant of the 1156, meaning it shares a base family with the 105 but differs in wattage, which is a critical distinction when substituting bulbs between these model years.
All four bulb types across the full specification range are ANSI-standardized for the US and Canadian markets and operate on a 12V electrical system.
The shift from the 631 to the 105 between the 1974 and 1975 model years represents a reduction in wattage from 21W to 13W for the engine compartment light position on the Ford F-250.