The Ford B-7000 uses the 1157 bulb for both front and rear turn signals across the 1983-1987 model years.
The 1157 is a dual-filament bulb, meaning it contains two separate filaments within a single envelope, allowing it to serve two distinct lighting functions at different wattages.
The bulb operates on a 12-volt electrical system and draws 21 watts on its high-intensity filament and 5 watts on its low-intensity filament.
The 1157 uses a BAY15d bayonet base, which features two offset pins positioned at different heights to prevent incorrect insertion into the socket.
The 1157 conforms to ANSI standards and is recognized for use in both the United States and Canada, reflecting a standardized specification shared across North American markets.
Because the same bulb number applies to both the front and rear turn signal positions on the Ford B-7000, a single replacement part covers all four turn signal sockets on the vehicle.
The BAY15d base is not interchangeable with single-pin bayonet bases such as the BA15s, and substituting a single-filament bulb in a dual-filament socket would result in incomplete circuit function.