Lincoln Mark IV Back Up Light Bulb Size

The Lincoln Mark IV back up light uses bulb sizes 1156, 1076, and P21W depending on the specific version. The provided data covers a range from 1972 through 1976.

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
1973-1976	1156
1972	1076

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, 8W.	1076

Other Locations

Additional Notes

The Lincoln Mark IV uses two distinct bulb types across its model years for the back up light position: the 1156 and the 1076.
The 1156 is the back up light bulb for the Lincoln Mark IV across the 1973-1976 model years.
Both the 1156 and 1076 are ANSI-standardized bulbs recognized in the United States and Canada, and both use a BA15s single-contact bayonet base.
The BA15s base designation indicates a 15mm bayonet fitting with a single contact point at the base, which determines physical socket compatibility.
Although the 1156 and 1076 share the same BA15s base type, they are not electrically interchangeable. The 1156 operates at 21W while the 1076 operates at 8W, a significant difference in power draw.
The 1972 Lincoln Mark IV uses the 1076 bulb, which at 8W produces noticeably less light output than the 21W 1156 used in later model years.
The 1076 is classified as a variant of the 1156, meaning the two share a common base design and 12V operating voltage but differ in wattage and intended application.
Substituting a 1156 in place of a 1076 in a 1972 Mark IV would introduce a higher current draw than the original circuit was specified for, due to the wattage difference between the two bulbs.