The Dodge Diplomat brake light utilizes 1157 and 2057 bulb sizes for the rear lighting system. Available information covers the production span from 1977 through 1989 for the specified vehicle components.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Dodge Diplomat uses the 1157 bulb for brake lighting across the majority of its model years, specifically 1977-1980 and 1982-1989.
The 1157 is a dual-filament bulb operating at 12V with a 21W high filament and 5W low filament, mounted on a BAY15d bayonet base, which allows it to serve both brake and tail light functions within a single housing.
The 1981 Dodge Diplomat brake light uses the 2057 bulb rather than the 1157 found in surrounding model years.
The 2057 shares the same BAY15d bayonet base as the 1157 but operates at higher wattages of 26.9W and 8W, making the two bulbs physically similar in base type while differing in output.
Although the 1157 and 2057 share the BAY15d base, substituting one for the other affects light output, and the specifications treat them as distinct fitments for specific model years.
The Center High Mount Stop Light (CHMSL) on the Dodge Diplomat uses the 921 bulb for 1987-1989 and the 1156 bulb for 1986.
The 921 is a single-filament wedge-type bulb in a T15 form factor, rated at 12V and 16W, and does not use a bayonet base, distinguishing it mechanically from the brake bulbs used elsewhere on the vehicle.
The 1156 used in the 1986 CHMSL position is a single-filament bulb with a BA15s bayonet base rated at 12V and 21W, and it is not interchangeable with the 921 due to the difference in base type.
All four bulb types listed in these specifications, the 1157, 2057, 921, and 1156, conform to ANSI standards applicable in both the United States and Canada.
The CHMSL position on the 1986 Dodge Diplomat uses the 1156, a single-filament bayonet bulb, while the standard brake light position on the same year uses the dual-filament 1157, reflecting different functional requirements between the two positions.