Ford F-100 Dome Light Bulb Size

The Ford F-100 dome light utilizes 561, 105, 1003, and 81 bulb sizes depending on the specific version of the vehicle. Available data covers the range from 1953 through 1980 for the specified lighting components.

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
1973-1980	561
1969-1972	105
1956-1968	1003
1953-1955	81

Bulb Specifications

Description	Bulb Size
ANSI standard (US & Canada). Festoon bulb, 44mm length, end-cap contacts. 12V, 12W.	561
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. 12V, 21W.	1003
ANSI standard (US & Canada). Single-filament bulb with BA15s bayonet base. 12V, 8W.	81

Other Locations

Additional Notes

The Ford F-100 dome light draws from three distinct bulb types across its model history: the 561 festoon, and the 1003, 105, and 81 single-filament bayonet types.
The 561 is a festoon-style bulb with a 44mm length and end-cap contacts, which means it seats by pressing lengthwise into spring clips rather than rotating into a socket. It operates at 12V and 12W.
The 1003, 105, and 81 bulbs all share the BA15s bayonet base, a single-pin mount that locks into its socket with a quarter-turn. Despite this shared base type, their wattage ratings differ significantly, ranging from 8W to 21W.
The Ford F-100 (1973-1980) uses the 561 festoon bulb for the dome light, making it physically incompatible with the BA15s bayonet sockets found in earlier model years.
The 1003 bulb, rated at 21W, is the highest-wattage dome light bulb in these specifications and was fitted across the longest continuous span of model years, covering 1956-1968.
The 105 bulb is described as a variant of the 1156, a widely available automotive bulb. It shares the BA15s base with the 1003 but draws only 13W compared to the 1003's 21W, meaning the two are not direct electrical equivalents despite their physical similarity.
The 81 bulb, used on the Ford F-100 (1953-1955), carries the lowest wattage of any dome light bulb in these specifications at 8W, while still using the BA15s bayonet base shared by the 105 and 1003.
All four bulb types in these specifications conform to ANSI standards applicable in both the United States and Canada.
Because the 105 and 1003 share the same BA15s base, physical fitment between the two is possible, but their differing wattage ratings make substitution a consideration that goes beyond socket compatibility alone.
The transition from the 1003 to the 105 occurred between the 1968 and 1969 model years, representing a reduction in dome light wattage from 21W to 13W while retaining the same base type.