The Ford C7000 front turn signal requires 1156 or 1157 bulb sizes, while rear turn signal applications use 1157, 1156, or 199 bulb sizes. The replacement chart covers 1971 through 1986 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 1156 and 1157 bulbs are the most frequently specified sizes across the Ford C7000 turn signal positions. The 1156 is a single-filament bulb operating at 12V and 21W with a BA15s bayonet base, while the 1157 is a dual-filament bulb sharing the same 12V rating but carrying a 21W/5W output split across its two filaments, seated in a BAY15d bayonet base.
The dual-filament design of the 1157 allows it to serve both turn signal and running light functions simultaneously through its two separate filaments, which is why it appears exclusively in the rear turn signal position for 1981-1986 model years.
The BA15s and BAY15d bayonet bases are physically distinct. The BA15s base used by the 1156 has a single locating pin, whereas the BAY15d base used by the 1157 has two offset pins. This offset pin arrangement on the BAY15d prevents incorrect filament alignment during installation, making the 1156 and 1157 non-interchangeable despite their similar appearance.
The 1982-1983 front turn signal position on the Ford C7000 specifies the 1157 rather than the 1156 used in surrounding years. Because the 1157 carries a dual-filament configuration and a different base type, substituting a 1156 in that position would not be a direct replacement.
The bulb designated 199 is classified as a variant of the 1156, sharing the same BA15s bayonet base, 12V operating voltage, and 21W single-filament output. It appears only in the 1971 rear turn signal position of the Ford C7000.
All three bulb types listed, the 1156, 1157, and 199, conform to ANSI standards recognized in both the United States and Canada, placing them within a standardized North American automotive lighting classification system.
The front and rear turn signal positions of the Ford C7000 do not share a consistent bulb type across the same model years. For 1984-1986, the front position uses the single-filament 1156 while the rear position uses the dual-filament 1157, requiring two different bulb types for a complete turn signal service on those vehicles.