International S2125 front turn signal bulbs use 1156 size while rear turn signal bulbs use 1157 size. The replacement chart covers 1980 to 1981 vehicle production years with corresponding bulb specifications.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The International S2125 uses the 1156 bulb for the front turn signal across the 1980-1981 model years.
The 1156 is an ANSI-standard single-filament bulb rated at 12V and 21W, fitted with a BA15s bayonet base.
The BA15s base is a single-contact bayonet mount, meaning it is not interchangeable with dual-contact bayonet bases without modification.
The rear turn signal on the International S2125 uses the 1157 bulb across the 1980-1981 model years.
The 1157 is an ANSI-standard dual-filament bulb rated at 12V with a 21W primary filament and a 5W secondary filament, fitted with a BAY15d bayonet base.
The BAY15d base features offset pins to prevent incorrect installation, distinguishing it physically from the BA15s base used by the 1156.
Because the 1156 and 1157 use different base types, BA15s and BAY15d respectively, the two bulbs are not interchangeable with each other.
The dual-filament design of the 1157 allows it to serve both a turn signal function and a secondary function such as a running or brake light within the same housing.
Both the 1156 and 1157 are recognized under ANSI standards applicable in the United States and Canada, indicating standardized physical and electrical specifications across manufacturers.