Ram 3500 Dome Light Bulb Size

The Ram 3500 dome light utilizes a 578 bulb size for interior illumination purposes within the cabin area. Available information covers a specific time span ranging from 2011 through 2024.

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
2023-2024	578
2011-2020	578

Bulb Specifications

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

Other Locations

Additional Notes

The Ram 3500 uses the 578 bulb size for the dome light across the 2011-2024 model years, with the exception of 2021 and 2022, which are not present in the specifications.
The 578 is a festoon-type bulb, meaning it is cylindrical in shape with metal end-cap contacts at each end rather than a base socket, and it seats by pressing lengthwise between two spring clips.
The 578 bulb has a specified length of 41mm, which is a critical fitment factor, as festoon bulbs must match the contact spacing of the housing to seat correctly.
The bulb operates at 12 volts and draws 12 watts, consistent with standard automotive interior lighting circuits.
The 578 designation follows ANSI standards recognized in both the United States and Canada, indicating a standardized specification for the bulb's electrical and physical characteristics.
Because festoon bulbs are available in multiple lengths, a replacement must match the 41mm specification of the 578; a bulb of a different length will not make proper contact in the fixture.