International 9370 front turn signal bulbs measure 1156 in size, while rear turn signal bulbs measure 1157 in size. The replacement chart covers vehicle production years spanning 1985 to 1987 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 9370 uses two distinct bulb types across its turn signal positions for the 1985-1987 model years: the 1156 at the front and the 1157 at the rear.
The 1156 is a single-filament bulb operating at 12V and 21W, built to ANSI standards for the US and Canadian markets, and fitted with a BA15s bayonet base.
The 1157 is a dual-filament bulb also rated at 12V, carrying separate filaments at 21W and 5W, and uses a BAY15d bayonet base under the same ANSI standard.
The BA15s base of the 1156 and the BAY15d base of the 1157 are not interchangeable. The BAY15d base features offset pins to prevent incorrect installation, while the BA15s base has symmetrical pins suited only to single-filament sockets.
The dual-filament design of the 1157 allows it to serve both a running light function at 5W and a turn or brake signal function at 21W within a single housing, whereas the 1156 supports only one function per socket.
Because the 1156 and 1157 share the same 12V operating voltage, the electrical system of the International 9370 is compatible with both bulb types without requiring separate voltage circuits for front and rear positions.
Substituting a 1156 in a rear socket designed for the 1157 would result in the loss of the low-wattage running light filament, as the 1156 carries no secondary filament to fulfill that role.