The Ford C800 front turn signal utilizes 1157 or 1156 bulb sizes while the rear turn signal requires a 1157 bulb size. The replacement chart covers 1980 through 1989 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 1157 bulb is the most frequently specified type across the Ford C800's turn signal positions, appearing in both front and rear applications across the majority of the 1980-1989 model range.
The 1157 is a dual-filament bulb operating at 12V with a 21W/5W output and a BAY15d bayonet base, conforming to ANSI standards recognized in both the United States and Canada.
The 1156 is a single-filament bulb operating at 12V with a 21W output and a BA15s bayonet base, also conforming to ANSI standards recognized in both the United States and Canada.
The key physical distinction between the 1157 and 1156 lies in their bayonet bases. The BAY15d base of the 1157 features offset locating pins to accommodate its dual-filament design, while the BA15s base of the 1156 uses a single-contact configuration suited to its single-filament construction.
Because the 1157 and 1156 use different base configurations, the two bulb types are not interchangeable despite their similar appearance and shared voltage rating.
The Ford C800 front turn signal position does not use a uniform bulb type across all years in the 1980-1989 range. The 1156 is specified for the front position in 1981, 1982, and 1984, while the 1157 is specified for all remaining years in that span.
The rear turn signal position on the Ford C800 uses the 1157 consistently across all listed model years from 1980 through 1989, making it the sole rear turn signal bulb type in the specifications.
In the front turn signal position, the 1984 model year is isolated in its use of the 1156, as the surrounding years 1983 and 1985-1989 all specify the 1157.
The dual-filament nature of the 1157 allows it to serve two lighting functions within a single housing, with the 21W filament typically handling the active turn signal function and the 5W filament serving a secondary role such as a parking or position light.
The single-filament 1156, specified for certain front turn signal years on the C800, provides only one active circuit, meaning the socket wiring in those applications is configured for a single-function output rather than the dual-function wiring associated with 1157 sockets.