Jeep J20 front and rear turn signal bulbs utilize either 1157 or 198 size specifications. The replacement chart covers vehicle production spanning 1974 to 1988.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Jeep J20 uses two distinct bulb types across its turn signal specifications: the 1157 and the 198, each with different electrical and physical characteristics.
The 1157 is a dual-filament bulb with a BAY15d bayonet base, rated at 12V with a 21W/5W output, meaning it operates one filament for running light duty and a second, brighter filament for the turn signal function.
The 198 is a miniature wedge bulb in a T5 form factor, rated at 12V and 2W, making it a single-filament, low-wattage unit with no bayonet base.
Both the 1157 and 198 conform to ANSI standards applicable in the United States and Canada.
The Jeep J20 front turn signal uses the 1157 bulb for model years 1979-1988 and the 198 bulb for model years 1974-1978.
The rear turn signal of the Jeep J20 follows the same pattern, with the 1157 specified for 1979-1988 and the 198 for 1974-1978.
Because the 1157 uses a BAY15d bayonet base and the 198 uses a wedge base, the two bulb types are not physically interchangeable with each other.
The wattage difference between the 1157 (21W/5W) and the 198 (2W) is substantial, and substituting one for the other would produce incorrect light output and could affect socket compatibility.
The front and rear turn signal positions share identical bulb specifications across all listed model years, indicating a consistent socket design between both positions within each generation.
The transition from the 198 to the 1157 across both front and rear positions occurred at the 1979 model year, reflecting a shift to a higher-wattage dual-filament configuration.