The Mack RWS front and rear turn signal bulbs both utilize a 1157 size. The replacement chart covers 1981 to 1985 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 Mack RWS uses the 1157 bulb for both front and rear turn signals across all listed model years, 1981-1985.
The 1157 is a dual-filament bulb, meaning it contains two separate filaments within a single glass envelope, allowing it to serve more than one lighting function.
The 1157 operates on a 12-volt electrical system and draws 21 watts on its high-intensity filament and 5 watts on its low-intensity filament.
The 1157 uses a BAY15d bayonet base, which features two offset pins at different heights to ensure correct orientation during installation and prevent incorrect seating.
The 1157 conforms to ANSI standards and is recognized in both the United States and Canada, reflecting a standardized specification shared across North American markets.
Because the same bulb number applies to both the front and rear turn signal positions on the Mack RWS, a single bulb type serves the full turn signal circuit on the vehicle.
The BAY15d base of the 1157 is not interchangeable with single-pin bayonet bases such as the BA15s, as the dual-pin offset configuration is specific to dual-filament applications.