Plymouth Horizon front side marker bulbs use 168 or 1157 bulb sizes, while rear side marker bulbs use 168 bulb size. The replacement chart covers vehicle production spanning 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 168 bulb for both front and rear side markers across the 1980-1990 model years, making it the dominant bulb type in these specifications.
The 168 is a T10 miniature wedge bulb rated at 12V and 4.9W, operating under the ANSI standard recognized in both the United States and Canada.
The wedge base of the 168 bulb requires no metal base or locking pins, as the glass envelope itself acts as the retention mechanism within the socket.
For the 1978-1979 Plymouth Horizon, the front side marker position calls for the 1157 bulb rather than the 168 used in later 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, and it also follows the ANSI standard for the US and Canada.
The BAY15d bayonet base of the 1157 features two offset pins, which prevent incorrect insertion and distinguish it physically from single-filament bayonet bulbs.
The 1157 and 168 are not interchangeable, as they differ in base type, wattage, filament count, and socket design.
The rear side marker position on the 1978-1979 Horizon uses the 168 bulb, meaning the front and rear positions on those model years require two different bulb types.