The Lincoln Mark VI high beam headlight bulb size measures H4651 or H5001, while low beam headlight bulb size measures H4656 or H5006. The replacement chart covers 1980 through 1983 vehicle 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 Lincoln Mark VI uses sealed beam headlight units across all four model years covered, meaning neither the high beam nor low beam positions accept replaceable bulbs. When a unit fails, the entire sealed assembly requires replacement.
Two distinct sealed beam formats appear across the 1980-1983 model years: a 4x6-inch rectangular unit and a 4-inch square or 5.75-inch round unit, depending on the position and year.
The 1982-1983 high beam position uses the H4651, a 4x6-inch rectangular sealed beam unit operating at 12V and conforming to ANSI standards recognized in both the United States and Canada.
The 1980-1981 high beam position uses the H5001, a 4-inch square sealed beam unit, also rated at 12V and built to the same ANSI standard. This format differs physically from the H4651 and the two units are not interchangeable.
The 1982-1983 low beam position uses the H4656, another 4x6-inch rectangular sealed beam unit at 12V. Although the H4651 and H4656 share the same physical form factor, they are distinct part numbers and serve different beam functions.
The 1980-1981 low beam position uses the H5006, a 5.75-inch round sealed beam unit at 12V. This unit differs in shape from the H5001 used in the high beam position for the same years, making the two non-interchangeable despite sharing a model year range.
All four bulb types carry ANSI standardization, which means they conform to a regulated specification governing electrical and physical characteristics for the North American market.
A notable shift in headlight configuration occurred between the 1981 and 1982 model years on the Lincoln Mark VI, with both the high and low beam positions transitioning from one sealed beam format to another across that boundary.