Mack WL Turn Signal Bulb Size

The Mack WL front and rear turn signal bulbs both utilize a 1157 size. The replacement chart covers 1982 to 1983 vehicle production specifications.

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
1982-1983	1157

Years	Bulb Size
1982-1983	1157

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

The 1157 is the bulb type specified for both the front and rear turn signals on the Mack WL across the 1982-1983 model years.
The 1157 is a dual-filament bulb, meaning it contains two separate filaments within a single envelope, allowing it to serve two distinct lighting functions at different wattages.
The 1157 operates on a 12-volt electrical system and draws 21 watts on its primary filament and 5 watts on its secondary filament.
The 1157 uses a BAY15d bayonet base, which is an offset twin-pin mount. The offset pin placement is a deliberate design feature that prevents incorrect insertion orientation.
The 1157 conforms to ANSI standards and is recognized across both the United States and Canada, reflecting a standardized specification shared between the two markets.
Because the same 1157 bulb type is specified for both the front and rear turn signal positions on the Mack WL, the same replacement unit is physically compatible with all four turn signal sockets on the vehicle.