Ram ProMaster City Map Light Bulb Size

The Ram ProMaster City map light requires bulb sizes 578 and 6461 depending on the specific vehicle configuration. Data for the bulb sizes covers the range from 2015 to 2022.

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
2022	578
2015-2020	6461

Bulb Specifications

Description	Bulb Size
ANSI standard (US & Canada). Festoon bulb, 41mm length, end-cap contacts. 12V, 12W.	578
ANSI standard (US & Canada). Festoon bulb, 36mm length, SV8.5 base. 12V, 5W.	6461

Other Locations

Additional Notes

The Ram ProMaster City map light circuit operates on 12 volts across all listed model years, which is standard for automotive interior lighting systems.
Both bulb types specified for the ProMaster City are festoon bulbs, a form factor characterized by a cylindrical glass tube with contacts at each end that seat into spring-loaded holders within the fixture.
The 6461 bulb is rated at 5 watts and measures 36mm in length with an SV8.5 base, which refers to a smooth-ended cap style with an 8.5mm cap width. It is the specified map light bulb for the 2015-2020 model years.
The 578 bulb is rated at 12 watts and measures 41mm in length with end-cap contacts. It is the specified bulb for the 2022 model year.
The two bulb types differ in both length and wattage. The 578 is 5mm longer and draws more than twice the wattage of the 6461, making the two types non-interchangeable despite sharing the same festoon form factor.
The SV8.5 base on the 6461 and the end-cap contacts on the 578 represent different contact configurations, which further distinguishes the physical fitment of each bulb within the map light housing.
Both the 578 and 6461 are classified under ANSI standards applicable in the United States and Canada, meaning their electrical and physical specifications conform to a defined industry standard rather than a proprietary designation.
The wattage difference between the two bulb types is relevant to the load placed on the vehicle's interior lighting circuit, as the 578 at 12 watts draws a notably higher current than the 6461 at 5 watts.