Peterbilt 389 Map Light Bulb Size

The Peterbilt 389 Map Light utilizes a 912 bulb size for illumination within the interior cabin area. Available information covers a specific time range starting in 2011 and ending in 2017.

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
2011-2017	912

Bulb Specifications

Description	Bulb Size
ANSI standard (US & Canada). Wedge bulb (T15). Variant of 921. 12V, 12W.	912

Other Locations

Additional Notes

The 912 bulb is the specified map light bulb size for the Peterbilt 389 across the 2011-2017 model years.
The 912 is an ANSI-standardized bulb type, meaning its physical and electrical characteristics conform to a defined North American specification recognized in both the United States and Canada.
The 912 uses a wedge base, designated T15, which refers to a tubular bulb body approximately 15 eighths of an inch wide that is held in its socket by the tension of the base contacts rather than by a bayonet or screw mechanism.
The 912 operates at 12 volts and draws 12 watts, which is consistent with standard automotive low-voltage electrical systems.
The 912 is a variant of the 921 bulb. While the two share the same T15 wedge form factor and 12-volt rating, they differ in wattage, as the 921 is rated at 18 watts versus the 912's 12 watts.
Because of the wattage difference between the 912 and the 921, substituting one for the other may affect circuit load and light output, even though the physical base is the same.