The Plymouth Horizon brake light requires a 1157 bulb size for proper illumination and function within the rear lighting assembly. Available data for the specified component covers the period from 1978 to 1990.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Plymouth Horizon uses the 1157 bulb for brake lighting across the 1978-1990 model years.
The 1157 is a dual-filament bulb with a BAY15d bayonet base, rated at 12V with a 21W high filament and a 5W low filament, conforming to ANSI standards for the US and Canadian markets.
The dual-filament design of the 1157 allows a single bulb to serve both brake and tail light functions, with the higher wattage filament activating under braking.
The BAY15d bayonet base of the 1157 features two offset pins, a physical characteristic that prevents incorrect installation of single-filament bulbs into the same socket.
The Center High Mount Stop Light on the Plymouth Horizon uses the 912 bulb for the 1986-1990 model years and the 1157 for the 1985 model year.
The 912 is a single-filament wedge-type bulb in the T15 form factor, rated at 12V and 12W, also conforming to ANSI standards for the US and Canadian markets.
The 912 is a variant of the 921 bulb, sharing the same wedge base and general form factor but differing in wattage output.
The Center High Mount Stop Light socket on the 1985 Plymouth Horizon accepts the 1157 with its BAY15d bayonet base, while the 1986-1990 socket accepts the 912 wedge base, making the two socket types physically incompatible with each other.