Ford F-150 Courtesy Bulb Size

The Ford F-150 courtesy component utilizes bulb sizes 578, 89, 912, and 105 across various applications within the provided data set. The recorded information spans a range from 1980 through 1998 for the specified vehicle lighting requirements.

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
1997-1998	578
1996	89
1995	912
1994	89
1991-1993	912
1988-1990	89
1981-1987	912
1980	105

Bulb Specifications

Description	Bulb Size
ANSI standard (US & Canada). Festoon bulb, 41mm length, end-cap contacts. 12V, 12W.	578
ANSI standard (US & Canada). Single-filament bulb with BA15s bayonet base. Lower wattage variant of 1156. 12V, 13W.	89
ANSI standard (US & Canada). Wedge bulb (T15). Variant of 921. 12V, 12W.	912
ANSI standard (US & Canada). Single-filament bulb with BA15s bayonet base. Variant of 1156. 12V, 13W.	105

Other Locations

Additional Notes

The Ford F-150 courtesy bulb specifications span model years 1980 through 1998, with three distinct bulb types appearing across that range: the 912 wedge bulb, the 89 bayonet bulb, and the 578 festoon bulb, plus a single appearance of the 105 bayonet bulb in 1980.
The 912 is the most frequently specified courtesy bulb across this range, covering the 1981-1987 and 1991-1992 model years. It is a T15 wedge bulb rated at 12V and 12W, and it is a variant of the 921 bulb.
The 89 bulb is specified for the 1988-1990 and 1994 and 1996 model years. It uses a BA15s bayonet base, operates at 12V and 13W, and is a lower-wattage variant of the 1156 bulb.
The 578 festoon bulb is specified for the 1997-1998 model years. At 41mm in length, it makes contact through end caps rather than a base socket, which distinguishes it physically from the wedge and bayonet types used in earlier years.
The 105 bulb, specified for the 1980 Ford F-150, shares the BA15s bayonet base and 12V, 13W rating with the 89 bulb, and is also a variant of the 1156. Despite these similarities, the 89 and 105 carry separate ANSI designations and are not listed as interchangeable within these specifications.
The 912 and 921 are related variants, but the specifications designate the 912 specifically for the applicable F-150 model years. Substituting a 921 without confirming fitment compatibility would not be supported by these specifications.
The three primary bulb types, 578, 89, and 912, each use a different base or contact style. The 578 uses end-cap contacts, the 89 uses a BA15s bayonet base, and the 912 uses a wedge fit. These differences mean the bulb types are not physically interchangeable with one another.
All four bulb types listed in the specifications conform to ANSI standards applicable in both the United States and Canada, indicating consistent regulatory classification across the range.
The 1993 and 1995 model years share the 912 specification with several earlier years, while the adjacent 1994 and 1996 years revert to the 89 bulb, reflecting non-consecutive alternation between bulb types during that period.
The 578 festoon bulb, used in the 1997-1998 model years, operates at 12W, matching the wattage of the 912 wedge bulb but differing from the 13W rating of the 89 and 105 bayonet bulbs.