Ram 4500 Dome Light Bulb Size

The Ram 4500 dome light uses a 578 bulb size for interior illumination. The replacement chart covers 2011 to 2012 production years with corresponding bulb specifications.

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
2011-2012	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 bulb is the sole dome light bulb type listed for the Ram 4500, covering the 2011-2012 model years.
The 578 is classified as a festoon bulb, a cylindrical lamp type that seats between two spring-loaded end-cap contacts rather than using a traditional socket base.
The 578 bulb has a 41mm length, which is the critical fitment factor for festoon bulbs, as the spring contacts must compress correctly to maintain a secure electrical connection.
The 578 operates at 12 volts and 12 watts, consistent with standard automotive interior lighting power requirements.
The 578 carries ANSI standardization recognized in both the United States and Canada, meaning the specification reflects a consistent North American fitment standard.