Ram 5500 Map Light Bulb Size

The Ram 5500 map light requires a 578 bulb size for proper installation within the interior overhead lighting housing. Data for the specified component covers the span from 2013 through 2018.

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
2013-2018	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 578 is the sole map light bulb size listed for the Ram 5500 across the 2013-2018 model years.
The 578 bulb follows the ANSI standard, which is the recognized specification authority for lighting components in the United States and Canada.
It is a festoon-type bulb, meaning it is cylindrical in form and seats between two spring-loaded end-cap contacts rather than fitting into a socket with a base pin or bayonet mount.
The 578 has a total length of 41mm, which is the critical fitment factor for festoon bulbs, as the housing span must match this length for the end-cap contacts to maintain a secure connection.
The bulb operates at 12 volts, consistent with the standard electrical system voltage found in passenger and commercial vehicles.
Its rated wattage is 12W, which reflects the power draw the vehicle's map light circuit is designed to accommodate for this application.
When replacing the map light bulb in the Ram 5500 (2013-2018), any substitute festoon bulb must match the 41mm length of the 578 to seat correctly within the fixture's contact points.