Ford F-250 Super Duty Dome Light Bulb Size

The Ford F-250 Super Duty dome light utilizes 578 and 912 bulb sizes for interior illumination. Available data covers the period from 1999 through 2016 for the specified vehicle 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
2005-2016	578
2002-2004	912
2000-2001	578
1999	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-250 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 metal end caps into spring-loaded holders rather than twisting or pushing 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 filament configuration depending on the specific variant.
Both the 578 and 912 are ANSI-standardized bulbs for the US and Canadian markets, meaning their physical and electrical specifications conform to a defined industry standard.
The Ford F-250 Super Duty uses the 578 festoon bulb for model years 2005-2016, representing the longer of the two production spans covered in these specifications.
The 912 wedge bulb is specified for the 1999, 2002-2004 model years, while the 578 festoon bulb is specified for 2000-2001, making those two consecutive years a notable switch back to the festoon format before the 912 returned in 2002.
Because the 578 and 912 use fundamentally different base types, a festoon holder and a wedge socket are not physically interchangeable, and substituting one bulb type for the other without a compatible socket is not possible.
Although the 912 is a variant of the 921, the two are not confirmed as direct drop-in replacements for this application, since wedge bulb variants within the same family can differ in filament position or wattage.