Mack CF Headlight Bulb Size

Additional Notes

• The Mack CF (1981-1991) was offered with three distinct headlamp configurations: a 2-round-lamp setup, a 4-rectangular-lamp setup, and a 4-round-lamp setup. Each configuration requires different bulb sizes for both high and low beam positions, making the physical lamp arrangement a critical factor in determining the correct replacement unit.
• All bulb types specified for the Mack CF across both beam positions are sealed beam units conforming to ANSI standards recognized in the United States and Canada. In a sealed beam design, the reflector, lens, and filament are fused into a single glass unit, so the entire assembly is replaced rather than an internal bulb.
• The H6024 is a 7-inch round sealed beam unit operating at 12V. On the Mack CF, it serves as both the high beam and low beam bulb in the 2-round-headlamp configuration across all years covered by the specifications, making it the only bulb type in this dataset that performs dual-beam duty within a single fitment.
• The 4-round-headlamp configuration uses the H5001 for high beam and the H5006 for low beam. The H5001 is a 4-inch square sealed beam unit, while the H5006 is a 5.75-inch round sealed beam unit, both rated at 12V. These two units are not interchangeable with each other despite sharing the same vehicle configuration.
• The 4-rectangular-headlamp configuration uses 4x6-inch rectangular sealed beam units across all positions, but the specific type varies by beam function and model year. The H4651 covers high beam throughout 1981-1991, while the low beam position alternates between the H4656 and the H4652 depending on the year.
• The H4652 is specified as a variant of the H4651, both being 4x6-inch rectangular sealed beam units at 12V. Despite their physical similarity, they are designated for different beam positions and are not listed as interchangeable within these specifications.
• The low beam rectangular fitment for the 4-rectangular-headlamp configuration shows year-specific variation: the H4652 is specified for 1982, 1985-1987, and 1990, while the H4656 is specified for 1981, 1983-1984, 1988-1989, and 1991. Substituting one for the other without confirming the correct year-specific designation would be inconsistent with the specifications.
• All six bulb types across the Mack CF specifications operate at 12V and comply with ANSI standards applicable in both the United States and Canada, indicating a consistent electrical system voltage and a standardized regulatory framework across the entire headlamp fitment range.