Buick Estate Wagon Headlight Bulb Size

Additional Notes

• The Buick Estate Wagon headlight specifications cover two distinct sealed beam form factors across the model's production span: the 4-inch square unit (H5001/H5006) used from 1959-1975, and the 4x6-inch rectangular unit (H4651/H4652/H4656) used from 1976-1983.
• All five bulb types listed in these specifications are ANSI-standard sealed beam units rated at 12V. In a sealed beam design, the reflector, lens, and filament are fused into a single glass unit, meaning the entire assembly is replaced rather than an internal bulb.
• The H5001 and H5006 are a matched high/low beam pair sharing the same 4-inch square sealed beam housing. The H5001 handles high beam duties, while the H5006 handles low beam duties across the 1959-1975 model years.
• The H4651 and H4652 are both 4x6-inch rectangular sealed beam units, with the H4652 described as a variant of the H4651. The H4651 serves the high beam position and the H4652 serves the low beam position, as seen in the 1980, 1982, and 1983 model years.
• The H4656 is a separate 4x6-inch rectangular sealed beam unit used exclusively in the low beam position for the Buick Estate Wagon during the 1976-1979 and 1981 model years, alongside the H4651 in the high beam position.
• The low beam specification for the Estate Wagon is not uniform across the 1976-1983 rectangular sealed beam era. The H4656 and H4652 alternate across those years, indicating that these two units are not interchangeable without confirming the specific model year.
• All bulb types across the full specification range conform to ANSI standards applicable in both the United States and Canada, meaning fitment is governed by standardized physical and electrical specifications rather than manufacturer-specific designs.
• The high beam specification for the Buick Estate Wagon remains constant within each major era: the H5001 covers all listed years from 1959-1975 without variation, and the H4651 covers all listed years from 1976-1983 without variation.