Mack CH Side Marker Bulb Size

The Mack CH front and rear side marker bulbs both utilize a 1891 bulb size. The replacement chart covers vehicle production spanning 1989 to 1997.

The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.

Front Side Marker

Years	Bulb Size
1989-1997	1891

Years	Bulb Size
1989-1997	1891

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

The Mack CH uses the 1891 bulb across all listed model years, 1989-1997, for both front and rear side marker positions.
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 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 and draws 2 watts, placing it among the lower-wattage bulbs used in commercial vehicle lighting applications.
The 1891 carries ANSI standardization, meaning its electrical and physical specifications are recognized across both the United States and Canada.
Because the same bulb number applies to both the front and rear side marker positions on the Mack CH, a single bulb type serves both locations on the vehicle.