Ford F-100 Back Up Light Bulb Size

The Ford F-100 back up light utilizes 1156, 199, and P21W bulb sizes depending on the specific production requirements for the vehicle lighting system. Data for the bulb specifications covers the range from 1969 to 1983.

The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.

Bulb Size by Year Range

Years	Bulb Size
1973-1983	1156
1971-1972	199
1969-1970	1156

Bulb Specifications

Description	Bulb Size
ANSI standard (US & Canada). Single-filament bulb with BA15s bayonet base. 12V, 21W.	1156
ANSI standard (US & Canada). Single-filament bulb with BA15s bayonet base. Variant of 1156. 12V, 21W.	199

Other Locations

Additional Notes

The Ford F-100 backup light bulb specifications cover model years 1969-1983, with two bulb types appearing across that range: the 1156 and the 199.
The 1156 is the dominant bulb type across these specifications, fitted to the Ford F-100 for 1969-1970 and again for 1973-1983.
The 1156 is an ANSI-standard single-filament bulb rated at 12V and 21W, mounted via a BA15s bayonet base, which uses a single locating pin to secure the bulb into its socket.
The 199 bulb is specified for the Ford F-100 in 1971-1972 only.
The 199 shares the same ANSI-standard BA15s bayonet base, 12V operating voltage, and 21W output as the 1156, and is formally classified as a variant of it.
Because the 199 is a variant of the 1156 and both share the BA15s base with identical voltage and wattage ratings, the two types are physically and electrically similar, though substitution should be confirmed against fitment data before use.
Both bulb types carry ANSI standardization applicable to the United States and Canada, meaning their specifications conform to a defined industry standard rather than being proprietary to a single manufacturer.
A single-filament design, as found in both the 1156 and 199, means the bulb serves one lighting function only, which is consistent with the dedicated role of a backup light.
The BA15s bayonet base designation indicates a 15mm base width with a single offset pin, a common automotive socket type that differs from the dual-pin BA15d base and is not interchangeable with it.