The International S1955 front turn signal uses a 1156 bulb size while the rear turn signal requires a 1157 bulb 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 S1955 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 base designation indicates a single-contact bayonet fitting with a 15mm base width, which is not interchangeable with dual-contact bayonet bases.
The rear turn signal on the International S1955 uses the 1157 bulb across the same 1981-1989 model year range.
The 1157 is a dual-filament bulb rated at 12V with two wattage outputs, 21W for the turn signal filament and 5W for the secondary filament, and it uses a BAY15d bayonet base.
The BAY15d base on the 1157 features offset pins to prevent incorrect installation, a design distinction that makes it physically incompatible with the BA15s base used by the 1156.
Because the 1156 and 1157 share a 12V operating voltage but differ in filament count and base type, the two bulbs are not interchangeable despite their similar appearance.
Both the 1156 and 1157 conform to ANSI standards applicable in the United States and Canada, indicating standardized electrical and physical specifications across those markets.