The Mack DMM front and rear turn signal bulbs both utilize a 1157 size bulb for illumination purposes. The replacement chart covers vehicle production spanning from 1981 to 1997.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Mack DMM uses the 1157 bulb for both its front and rear turn signals across all model years from 1981-1997.
The 1157 is a dual-filament bulb, meaning it contains two separate filaments within a single glass envelope, each rated for a different wattage.
The two filaments in the 1157 are rated at 21W and 5W respectively, with the higher-wattage filament typically serving the turn signal or brake function and the lower-wattage filament serving as a running light.
The 1157 operates on a 12V electrical system, which is standard for automotive applications in this vehicle class.
The 1157 uses a BAY15d bayonet base, a two-pin offset base design that prevents incorrect installation by ensuring the bulb can only be seated in one orientation.
The 1157 conforms to ANSI standards and is recognized in both the United States and Canada, reflecting its widespread adoption across North American vehicle applications.
Because the same bulb number is specified for both the front and rear turn signal positions, a single bulb type serves the full turn signal circuit on the DMM.