Ford Fairmont Back Up Light Bulb Size

The Ford Fairmont back up light requires bulb size P21W or 1156 depending on the specific version. Available information covers the period from 1978 through 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
1978-1983	1156

Bulb Specifications

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

Other Locations

Additional Notes

The Ford Fairmont uses the 1156 bulb across all listed model years, spanning 1978-1983, for the back up light position.
The 1156 is an ANSI-standardized bulb type, meaning its physical and electrical specifications are governed by a recognized North American standard shared across the United States and Canada.
This bulb operates on a 12-volt electrical system and draws 21 watts, which is consistent with standard incandescent automotive reverse lighting of that era.
The 1156 is a single-filament bulb, meaning it serves only one lighting function, as opposed to dual-filament types that handle two functions such as braking and running light simultaneously.
The BA15s designation refers to a bayonet-style base with a 15mm collar and a single locating pin, which determines physical fitment into the socket and is not interchangeable with double-pin bayonet variants such as the BA15d.
Any replacement bulb for the Ford Fairmont back up light must match the BA15s single-pin base configuration, as substituting a visually similar bulb with a different base type will result in incorrect fitment.