Mack Mid-Liner CS Series Turn Signal Bulb Size

The Mack Mid-Liner CS Series front and rear turn signal bulb size is 1157. The replacement chart covers vehicle production from 1986 to 1997.

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

Front Turn Signal

Years	Bulb Size
1986-1997	1157

Years	Bulb Size
1986-1997	1157

Description	Bulb Size
ANSI standard (US & Canada). Dual-filament bulb with BAY15d bayonet base. 12V, 21W/5W.	1157

The Mack Mid-Liner CS Series uses the 1157 bulb for both front and rear turn signals across all model years from 1986-1997.
The 1157 is a dual-filament bulb, meaning it contains two separate filaments within a single glass envelope, rated at 21W for the high-intensity filament and 5W for the low-intensity filament.
It operates on a 12-volt electrical system, which is standard for automotive and light commercial vehicle applications.
The 1157 uses a BAY15d bayonet base, a two-pin offset base design that prevents incorrect installation by ensuring the pins are not symmetrically placed.
The 1157 is classified under the ANSI standard and is recognized in both the United States and Canada, reflecting a standardized specification shared across North American markets.
Because the front and rear turn signal positions share the same bulb type, a single 1157 bulb serves as a direct replacement for either position on this vehicle.
The dual-filament design of the 1157 makes it suitable for combined functions, such as serving as both a turn signal and a running or brake light within the same housing, depending on circuit configuration.