Mack MH Headlight Bulb Size

Mack MH headlight bulb size specifications include high beam options of H6024, H4651, and H5001, along with low beam alternatives of H6024, H4656, and H5006 bulb sizes. The replacement chart covers vehicle production years spanning 1983 to 1994.

The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.

High Beam Headlight

Years	Bulb Size
1983-1994	H6024 (With 2 Round Headlamps)
	H4651 (With 4 Rectangular Headlamps)
	H5001 (With 4 Round Headlamps)

Low Beam Headlight

Years	Bulb Size
1992-1994	H6024 (With 2 Round Headlamps)
	H4656 (With 4 Rectangular Headlamps)
	H5006 (With 4 Round Headlamps)
1988-1991	H6024 (With 2 Round Headlamps)
	H4652 (With 4 Rectangular Headlamps)
	H5006 (With 4 Round Headlamps)
1987	H6024 (With 2 Round Headlamps)
	H4656 (With 4 Rectangular Headlamps)
	H5006 (With 4 Round Headlamps)
1985-1986	H6024 (With 2 Round Headlamps)
	H4652 (With 4 Rectangular Headlamps)
	H5006 (With 4 Round Headlamps)
1984	H6024 (With 2 Round Headlamps)
	H4656 (With 4 Rectangular Headlamps)
	H5006 (With 4 Round Headlamps)
1983	H6024 (With 2 Round Headlamps)
	H4652 (With 4 Rectangular Headlamps)
	H5006 (With 4 Round Headlamps)

Bulb Specifications

Description	Bulb Size
ANSI standard (US & Canada). 7-inch round sealed beam unit. Not a replaceable bulb — the entire unit is replaced. 12V.	H6024
ANSI standard (US & Canada). 4x6-inch rectangular sealed beam unit. Not a replaceable bulb — the entire unit is replaced. 12V.	H4651
ANSI standard (US & Canada). 4-inch square sealed beam unit. Not a replaceable bulb — the entire unit is replaced. 12V.	H5001
ANSI standard (US & Canada). 4x6-inch rectangular sealed beam unit. Not a replaceable bulb — the entire unit is replaced. 12V.	H4656
ANSI standard (US & Canada). 5.75-inch round sealed beam unit. Not a replaceable bulb — the entire unit is replaced. 12V.	H5006
ANSI standard (US & Canada). 4x6-inch rectangular sealed beam unit, variant of H4651. Not a replaceable bulb — the entire unit is replaced. 12V.	H4652

Other Locations

Additional Notes

The Mack MH uses three distinct headlamp configurations across its 1983-1994 model range: a 2-round-headlamp setup, a 4-rectangular-headlamp setup, and a 4-round-headlamp setup. Each configuration requires a different set of bulb sizes, and the correct fitment is determined entirely by which headlamp arrangement is present on the vehicle.
All bulb types specified for the Mack MH are sealed beam units conforming to ANSI standards recognized in both the United States and Canada. 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 element.
The H6024 is a 7-inch round sealed beam unit operating at 12V. It serves as both the high beam and low beam on the 2-round-headlamp configuration across all model years in the specifications, making it the only bulb type in this dataset that performs dual beam functions within a single fitment position.
The 4-round-headlamp configuration uses the H5001 for high beam and the H5006 for low beam throughout 1983-1994. 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.
The 4-rectangular-headlamp configuration uses 4x6-inch rectangular sealed beam units for both beam positions. The high beam position takes the H4651 across all years, while the low beam position is filled by either the H4652 or H4656 depending on the model year.
The H4652 is specified as a variant of the H4651. Despite sharing the same 4x6-inch rectangular sealed beam form factor and 12V rating, the H4652 and H4651 carry distinct ANSI designations, which indicates they are not interchangeable between beam positions.
For the low beam position in the 4-rectangular-headlamp configuration, the H4656 is specified for 1983, 1984, 1987, 1992, 1993, and 1994, while the H4652 is specified for 1985, 1986, 1988, 1989, 1990, and 1991. Both are 4x6-inch rectangular sealed beam units at 12V, but substituting one for the other without confirming the correct ANSI designation for the given year would be inconsistent with the specifications.
Because all units in these specifications are sealed beams governed by ANSI standards, physical form factor alone does not confirm interchangeability. The ANSI designation encodes beam pattern and photometric output characteristics, so two units of the same physical size but different designations, such as H4651 and H4656, are specified for different beam functions and are not listed as interchangeable within these specifications.