The Plymouth Reliant brake light utilizes 2057 and 1157 bulb sizes depending on the specific production version. Provided information covers a span of time starting in 1981 and ending in 1989.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Plymouth Reliant brake light circuit uses the 2057 bulb for model years 1982-1989, making it the dominant fitment across the vehicle's production run for that function.
The 2057 is a dual-filament bulb with a BAY15d bayonet base, rated at 12V with a high/low filament draw of 26.9W and 8W respectively, conforming to ANSI standards recognized in both the United States and Canada.
The 1981 Plymouth Reliant brake light uses the 1157 bulb, which shares the same BAY15d bayonet base as the 2057 but operates at lower wattage, rated at 12V with filaments drawing 21W and 5W.
Because the 2057 and 1157 share the BAY15d bayonet base, they are physically interchangeable in socket fitment, though their filament wattages differ, with the 2057 producing a notably brighter output on its high filament.
The center high mount stop light on the Plymouth Reliant is specified for model years 1986-1989 and uses the 921 bulb exclusively for that position.
The 921 is a single-filament wedge-type bulb in a T15 form factor, rated at 12V and 16W, and carries ANSI certification for the US and Canadian markets.
The wedge base of the 921 is mechanically incompatible with the BAY15d bayonet base used by the 2057 and 1157, meaning the center high mount stop light socket does not accept the same bulbs used in the standard brake light positions.