The Mack WL uses 1891 bulb size for both front and rear side marker applications. The replacement chart covers 1982 to 1983 vehicle production years with corresponding bulb size specifications.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The 1891 bulb is the sole bulb type specified across all side marker positions on the Mack WL for the 1982-1983 model years.
The 1891 is classified as a T5 miniature wedge bulb, a designation that refers to its tubular glass envelope measuring 5/8 of an inch in width.
The wedge base design means the 1891 is held in its socket by the pinched glass base itself, 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 used in automotive marker lighting applications.
The 1891 carries ANSI standardization recognized in both the United States and Canada, meaning its electrical and physical specifications conform to a defined industry standard in both markets.
The same 1891 bulb type is specified for both the front and rear side marker positions on the Mack WL, indicating interchangeability between those two locations.