Ford E-450 Super Duty Dome Light Bulb Size

The Ford E-450 Super Duty dome light utilizes bulb sizes 578, 912, and 6411 across various production periods. Available information covers the specific time span from 2003 through 2023.

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
2021-2023	578
2008-2019	912
2005-2007	578
2004	6411
2000-2003	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
ANSI standard (US & Canada). Festoon bulb, 36mm length, SV8.5 base. 12V, 5W.	6411

Other Locations

Additional Notes

The Ford E-450 Super Duty dome light draws from three distinct bulb types across its model years: the 578, the 912, and the 6411, all of which conform to ANSI standards recognized in the United States and Canada.
The 912 is the most frequently specified bulb across the Ford E-450 Super Duty dome light fitments, appearing in model years 2000-2003, 2008-2019, covering the majority of the vehicle's production span in these specifications.
The 912 is a T15 wedge-base bulb rated at 12V and 12W. It is classified as a variant of the 921 bulb, meaning the two share a close relationship in physical form, though they are not unconditionally interchangeable in all applications.
The 578 is a festoon-style bulb with end-cap contacts and a 41mm length, rated at 12V and 12W. It is specified for the Ford E-450 Super Duty in model years 2005-2007 and 2021-2023.
Festoon bulbs make contact at both ends of the cylindrical body rather than through a base, which distinguishes their socket type from wedge-base designs. The 578 and 6411 both follow this festoon format, but they are not interchangeable due to differing lengths.
The 6411 festoon bulb carries an SV8.5 base designation and a 36mm length, making it physically shorter than the 578. It is rated at 12V but only 5W, a notably lower wattage than either the 578 or the 912.
The 6411 is specified exclusively for the 2004 Ford E-450 Super Duty dome light, setting that model year apart from all others in these specifications in terms of both bulb format and wattage output.
The 578 and 912 share the same 12V, 12W electrical rating, but their physical formats differ entirely. The 578 uses end-cap festoon contacts while the 912 uses a wedge base, making them incompatible with each other's sockets despite identical voltage and wattage figures.
Model years 2005-2007 and 2021-2023 both use the 578 bulb, while the intervening years 2008-2019 revert to the 912. This reflects socket-level changes in the dome light housing across different production periods of the E-450 Super Duty.
When sourcing a replacement dome light bulb for the Ford E-450 Super Duty, the bulb size must correspond precisely to the socket type installed in that specific model year, as the festoon and wedge formats require physically different housings.