Mack WL License Plate Bulb Size

The Mack WL license plate light requires a unique 1891 bulb size for proper installation and function. Data for the specific lighting component covers the range from 1982 to 1983.

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
1982-1983	1891

Bulb Specifications

Description	Bulb Size
ANSI standard (US & Canada). Miniature wedge bulb (T5). 12V, 2W.	1891

Other Locations

Additional Notes

The 1891 is the bulb type specified for the license plate position on the Mack WL across both listed model years, 1982-1983.
The 1891 is classified as a miniature wedge bulb, using a T5 envelope, which refers to a tubular glass shape roughly 5/8 of an inch wide.
The wedge base design means the bulb is held in place by the socket gripping the glass base directly, with no separate metal base or pins involved.
The 1891 operates at 12 volts, consistent with standard automotive electrical systems of that era.
At a rated 2 watts, the 1891 draws very low current, which is typical for license plate illumination where output requirements are minimal.
The 1891 carries ANSI standardization recognized in both the United States and Canada, meaning the specification conforms to a defined interindustry standard rather than a proprietary fitment.