The Ford C700 front and rear turn signal bulbs utilize 1156 and 1157 sizes. The replacement chart covers 1980 to 1986 production years 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 Ford C700 turn signal specifications cover model years 1980-1986, with two bulb types appearing across both front and rear positions: the 1156 and the 1157.
Both the 1156 and 1157 are ANSI-standardized bulbs recognized in the United States and Canada, operating on a 12-volt electrical system.
The 1156 is a single-filament bulb rated at 21W, fitted with a BA15s bayonet base, which has a single locating pin on its collar.
The 1157 is a dual-filament bulb rated at 21W and 5W, fitted with a BAY15d bayonet base, which uses two offset locating pins to prevent incorrect insertion.
Because the BA15s and BAY15d bases are physically distinct, the 1156 and 1157 are not interchangeable despite sharing the same primary wattage rating of 21W.
The Ford C700 front turn signal position used the 1156 for model years 1982 and 1984-1986, while the 1157 was specified for 1980-1981 and 1983, indicating the socket type at that position varied across the production run.
The rear turn signal position of the Ford C700 used the 1157 consistently across 1981-1986, with the 1156 specified only for the 1980 model year.
The dual-filament design of the 1157 allows it to serve both a steady running-light function at 5W and a flashing turn signal function at 21W within a single bulb, which is why it is commonly found in combined rear lamp assemblies.
Installations requiring the 1157 cannot accept the 1156 as a substitute, since the single-filament 1156 lacks the second filament circuit that a dual-function socket is wired to use.