International S1853 front turn signal bulbs use 1156 size while rear turn signal bulbs use 1157 size. The replacement chart covers vehicle production spanning 1981 to 1989.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The International S1853 uses the 1156 bulb for the front turn signal across all documented model years, spanning 1981-1989.
The 1156 is a single-filament bulb operating at 12V and 21W, fitted with a BA15s bayonet base, and recognized under ANSI standards in both the United States and Canada.
The BA15s bayonet base features a single contact pin, which physically prevents substitution with dual-filament bayonet bulbs that use offset pins.
The rear turn signal on the International S1853 uses the 1157 bulb across all documented model years, spanning 1981-1989.
The 1157 is a dual-filament bulb rated at 12V with two wattage outputs, 21W for the high-intensity filament and 5W for the low-intensity filament, also recognized under ANSI standards in the United States and Canada.
The 1157 uses a BAY15d bayonet base, which has two offset contact pins corresponding to its two filaments, making it incompatible with the BA15s socket used by the 1156.
Although the 1156 and 1157 share the same 12V operating voltage and the same 21W rating on their primary filament, the difference in base type means the two bulbs are not interchangeable between front and rear sockets on the S1853.
The dual-filament design of the 1157 at the rear allows a single bulb to serve more than one lighting function, with the lower 5W filament typically serving as a running or parking light alongside the 21W turn signal filament.