The Ford LTD headlight bulb specifications include H4651 and H5001 sizes for high beam applications, along with H4656, H4652, and H5006 sizes for low beam functions across this model line. The replacement chart covers 1965 through 1986 production years with corresponding bulb size data.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Ford LTD headlight specifications span 1965-1986 and reference five distinct sealed beam unit types: H4651, H4652, H4656, H5001, and H5006. All five conform to ANSI standards recognized in both the United States and Canada and operate at 12V.
Sealed beam units are self-contained assemblies in which the filament, reflector, and lens are fused into a single housing. None of the five bulb types listed for the Ford LTD accept a replaceable internal bulb; the entire unit is exchanged upon failure.
The H5001 and H5006 are the most frequently specified types across the full range, covering the high beam and low beam positions respectively for model years 1965-1978. The H5001 is a 4-inch square sealed beam unit, while the H5006 is a 5.75-inch round sealed beam unit, making the two physically incompatible with each other despite serving paired functions in the same headlight system.
From 1979 onward, the Ford LTD transitioned to 4x6-inch rectangular sealed beam units for both beam positions. The H4651 serves the high beam role across 1979-1986, whereas the low beam position uses H4652, H4656, or both depending on the specific year.
The H4652 is specified as a variant of the H4651. Both are 4x6-inch rectangular sealed beam units, yet they are assigned to separate beam positions and are not listed as interchangeable within these specifications.
The low beam position on the Ford LTD shows the greatest variation across the full production span. Three different rectangular sealed beam types appear in that position for 1979-1986 alone: H4652 covers 1979 and 1981-1985, while H4656 is specified for 1980 and 1986, indicating that the same calendar year range does not guarantee a uniform low beam fitment.
The H4656 and H4652 are both 4x6-inch rectangular sealed beam units, yet they carry distinct ANSI designations and are assigned to different model years in the low beam position. Substituting one for the other is not supported by these specifications.
The shift from round and square sealed beam formats to the 4x6-inch rectangular format occurred at the 1979 model year for the Ford LTD, aligning with the broader industry adoption of rectangular sealed beam headlights that followed regulatory changes in the United States during the late 1970s.