The Dodge St. Regis front turn signal bulb accommodates 3 sizes: 2057, 1157NA, and 1157, while the rear turn signal bulb uses either 2057 or 1157. A replacement chart documents bulb specifications across the 1979 to 1981 production range.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Dodge St. Regis turn signal specifications span the 1979-1981 model years, covering both front and rear positions across three distinct bulb types: 1157, 1157NA, and 2057.
All three bulb types used in the St. Regis turn signal system share the BAY15d bayonet base, an offset dual-pin base design that physically prevents incorrect insertion of a single-filament bulb into a dual-filament socket.
The dual-filament construction present in all three bulb types serves two circuits within a single housing, typically supporting both the turn signal function on the higher-wattage filament and a secondary running or parking light function on the lower-wattage filament.
The 1157 and 1157NA types operate at 21W on the high filament and 5W on the low filament, while the 2057 operates at 26.9W on the high filament and 8W on the low filament, making the 2057 a higher-output variant despite sharing the same base type.
Because the 1157, 1157NA, and 2057 all use the identical BAY15d base, they are physically interchangeable, though substituting one for another may alter light output or color output from the original specification.
The 1157NA fitted to the 1980 Dodge St. Regis front turn signal is distinguished from the standard 1157 by its natural amber glass envelope, which produces an amber signal output without relying on a colored lens or housing to filter a clear bulb.
The rear turn signal on the 1980 St. Regis uses the standard 1157, while the front uses the 1157NA, indicating that the amber coloring for the front signal was achieved at the bulb level rather than through the lens on that model year.
For the 1981 model year, both the front and rear turn signal positions on the St. Regis share the same 2057 specification, representing a uniform fitment across both positions that was not present in the 1979 or 1980 model years.
All bulb types in these specifications conform to ANSI standards recognized in both the United States and Canada, indicating standardized electrical and photometric performance requirements across those markets.
The 1979 St. Regis uses the 1157 in both the front and rear turn signal positions, making it the only model year in these specifications where a single bulb type covers all turn signal positions without variation.