Ford B-700 front turn signal bulbs use 1157 size while rear turn signal bulbs use 1156 or 1157 size. The replacement chart covers vehicle production years spanning 1980 to 1994.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Ford B-700 front turn signal position uses the 1157 bulb across all listed model years from 1980-1994.
The 1157 is a dual-filament bulb operating at 12V with a 21W/5W output rating and a BAY15d bayonet base, conforming to ANSI standards recognized in the US and Canada.
The dual-filament design of the 1157 allows it to serve two lighting functions within a single housing, with the higher 21W filament handling the turn signal function and the lower 5W filament serving a secondary role such as a parking light.
The Ford B-700 rear turn signal position uses the 1157 bulb from 1980-1989, then transitions to the 1156 bulb for 1990-1994.
The 1156 is a single-filament bulb operating at 12V with a 21W output rating and a BA15s bayonet base, also conforming to ANSI standards recognized in the US and Canada.
Although the 1156 and 1157 share the same 21W primary filament output and a visually similar bayonet base profile, their bases are not interchangeable. The BA15s base of the 1156 has a single contact pin, while the BAY15d base of the 1157 has two offset contact pins.
The pin offset on the BAY15d base of the 1157 is a deliberate design feature that prevents incorrect filament alignment, meaning the bulb can only be seated in one orientation within its socket.
Substituting a 1157 into a socket designed for the 1156 is not possible due to the physical difference in base configuration, even though the bulbs share the same primary wattage.