Mack CF License Plate Bulb Size

The Mack CF license plate light requires a single 1891 bulb size for proper illumination of the rear vehicle identification area. Available data for the specified lighting component covers the range from 1981 to 1991.

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
1981-1991	1891

Bulb Specifications

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

Other Locations

Additional Notes

The Mack CF uses the 1891 bulb for the license plate position across all listed model years, spanning 1981-1991.
The 1891 is classified as a T5 miniature wedge bulb, a designation that refers to its tubular glass envelope with a width of 5/8 inch.
The wedge base design means the 1891 bulb is held in place by the socket gripping the base of the glass envelope directly, with no separate metal base or pins involved.
The 1891 operates at 12 volts and draws 2 watts, placing it among the lower-wattage bulbs in automotive applications, consistent with the low-intensity requirements of a license plate lamp.
The 1891 carries ANSI standardization recognized in both the United States and Canada, meaning the bulb conforms to a defined specification rather than a proprietary one.
Because the 1891 is a wedge-type bulb, it is not interchangeable with bayonet or screw-base bulbs of similar size without a socket adapter.