Ford LTD Back Up Light Bulb Size

The Ford LTD back up light utilizes 1156 and P21W bulb sizes depending on the specific production requirements for the vehicle. Available data covers the range from 1965 to 1986.

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
1965-1986	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 LTD uses the 1156 bulb for the back up light across all listed model years from 1965 to 1986.
The 1156 is a single-filament bulb, meaning it serves one lighting function rather than combining two, such as stop and tail, into a single unit.
It operates on a 12-volt electrical system and draws 21 watts, which is consistent with standard automotive incandescent output for reverse lighting applications.
The 1156 uses a BA15s bayonet base, where "BA15s" denotes a single-contact bayonet fitting with a 15mm base width.
The bulb conforms to ANSI standards and is specified for use in the United States and Canada, indicating it meets the regulatory and performance requirements of both markets.
Because the same bulb number applies to the Ford LTD without variation across all 22 listed model years, the 1156 is a consistent fitment for this vehicle throughout its production span in the specifications.
The BA15s base is not interchangeable with the BA15d base, which is a dual-contact bayonet fitting used on double-filament bulbs. Substituting one for the other is not possible without a socket adapter.