The International 4600LP front turn signal requires a 1156 bulb size while the rear turn signal uses a 1157 bulb size. The replacement chart covers 1992 to 1994 vehicle production years with corresponding bulb size specifications.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The International 4600LP uses two distinct bulb types across its turn signal positions for the 1992-1994 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, fitted with a BA15s bayonet base, and is recognized under ANSI standards in both the United States and Canada.
The 1157 is a dual-filament bulb rated at 12V with two wattage outputs, 21W and 5W, fitted with a BAY15d bayonet base, and also carries ANSI recognition in the United States and Canada.
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 a single contact pin centered at the base.
Because the 1156 is a single-filament bulb and the 1157 is a dual-filament bulb, substituting one for the other would result in incorrect circuit behavior regardless of any physical fitment considerations.
The dual-filament design of the 1157 allows it to serve two independent functions within a single housing, with the 21W filament typically assigned to the turn signal function and the 5W filament to a secondary function such as a running or position light.
Both the 1156 and 1157 operate on a 12V electrical system, which is consistent with the standard automotive electrical architecture found in commercial vehicles of the 1992-1994 period.