Cadillac Calais headlight bulbs utilize H4651, H5001 sizes for high beam and H4656, H4652, H5006 sizes for low beam applications. The replacement chart covers 1965 through 1976 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 Cadillac Calais headlight specifications span the 1965-1976 model years, covering both high beam and low beam positions across two distinct sealed beam form factors.
The H5001 and H5006 are the most frequently specified bulbs in these listings. The H5001 is a 4-inch square sealed beam unit used for high beam, while the H5006 is a 5.75-inch round sealed beam unit used for low beam. Both are ANSI-standardized 12V units and appear across the 1965-1974 model years in their respective positions.
All bulb types listed for the Cadillac Calais are sealed beam units, meaning the lens, reflector, and filament are fused into a single assembly. Replacement requires substituting the entire unit rather than an internal bulb.
For the 1975-1976 model years, the Calais transitioned from square and round sealed beam units to 4x6-inch rectangular sealed beam units, with the high beam position using the H4651 across both years.
The low beam position shows variation across the 1975 and 1976 model years specifically. The 1975 model uses the H4652, which is a variant of the H4651, while the 1976 model uses the H4656. Although both are 4x6-inch rectangular sealed beam units, they are distinct part numbers and are not interchangeable.
The H5001 high beam and H5006 low beam units are not interchangeable with each other despite both being ANSI-standard sealed beam types, as they differ in physical form factor and beam function.
All bulb types across the full 1965-1976 range operate at 12V, consistent with standard automotive electrical systems of that period.
The ANSI standardization of all listed bulb types means equivalent units from different manufacturers sharing the same ANSI designation are generally considered interchangeable, provided the form factor and voltage rating match.