The Ford L9501 front turn signal uses a 1157 bulb size while the rear turn signal requires a 1156 bulb size. The replacement chart covers vehicle production spanning 1997 to 1998.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Ford L9501 uses two distinct bulb types across its turn signal positions: the 1157 for the front and the 1156 for the rear, covering both the 1997-1998 model years.
The 1157 bulb is a dual-filament type, operating at 12V with a 21W main filament and a 5W secondary filament, which allows it to serve both signaling and parking light functions from a single housing.
The 1156 bulb is a single-filament type rated at 12V and 21W, dedicated solely to its assigned circuit without a secondary filament.
The 1157 uses a BAY15d bayonet base, which features two offset pins at different heights to prevent incorrect insertion of a single-filament bulb into a dual-filament socket.
The 1156 uses a BA15s bayonet base, which has a single pin and is not physically compatible with a BAY15d socket, making the front and rear bulbs non-interchangeable despite sharing the same voltage and primary wattage.
Both the 1157 and 1156 are classified under ANSI standards and are recognized across the United States and Canada, placing them within a widely distributed specification framework.
Although the 1157 and 1156 share the same 21W primary output, substituting one for the other is not possible due to the differing base configurations and filament counts.