Ford F-450 Super Duty Dome Light Bulb Size

The Ford F-450 Super Duty dome light utilizes bulb sizes 578 and 912 according to the provided specifications. Available information covers the range from 1999 through 2016.

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
2005-2016	578
2004	912
2002-2003	578
1999-2001	912

Bulb Specifications

Description	Bulb Size
ANSI standard (US & Canada). Festoon bulb, 41mm length, end-cap contacts. 12V, 12W.	578
ANSI standard (US & Canada). Wedge bulb (T15). Variant of 921. 12V, 12W.	912

Other Locations

Additional Notes

The Ford F-450 Super Duty dome light uses one of two bulb types across its model years: the 578 festoon bulb or the 912 wedge bulb, both rated at 12V and 12W.
The 578 is a festoon-style bulb measuring 41mm in length with end-cap contacts, meaning it seats by pressing its two flat metal ends into spring clips rather than inserting into a socket.
The 912 is a T15 wedge-base bulb and a variant of the more widely available 921, sharing the same base type but differing in output or construction details depending on the manufacturer.
Both the 578 and 912 are ANSI-standardized bulbs recognized in the US and Canada, meaning their physical and electrical specifications conform to a defined industry standard.
The Ford F-450 Super Duty uses the 578 festoon bulb for model years 2002-2003 and 2005-2016, covering the majority of the production range in these specifications.
The 912 wedge bulb is specified for the Ford F-450 Super Duty for model years 1999-2001 and 2004, representing a non-consecutive fitment pattern within the broader range.
Because the 578 and 912 use fundamentally different base types, a festoon clip mount and a wedge socket respectively, the two bulbs are not interchangeable with each other regardless of their identical voltage and wattage ratings.
The 2004 model year uses the 912 wedge bulb, while the immediately adjacent 2003 and 2005 model years use the 578 festoon bulb, making 2004 an isolated exception within an otherwise consistent fitment period.