The Mack RWL front and rear turn signal bulbs both utilize a 1157 size bulb for replacement applications. The replacement chart covers vehicle production spanning 1981 to 1985.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Mack RWL uses the 1157 bulb in both the front and rear turn signal positions across the 1981-1985 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 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 filament activation.
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 bulb number applies to both the front and rear turn signal positions for all listed model years, a single bulb type services the entire turn signal circuit on the RWL.