The GMC C25 Suburban headlight bulb specifications include H6024 and H5001 sizes for high beam applications, along with H6024 and H5006 sizes for low beam functions. The replacement chart covers 1967 to 1978 model 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 GMC C25 Suburban uses two distinct sealed beam configurations across its 1967-1978 model range. Vehicles from 1967-1972 use a four-lamp system with separate high and low beam units, while 1973-1978 models use a single H6024 unit that serves both functions.
The H6024 is a 7-inch round sealed beam unit operating at 12V and conforming to ANSI standards recognized in both the United States and Canada. It is the specified bulb for both the high beam and low beam positions on the 1973-1978 GMC C25 Suburban.
The H5001 is a 4-inch square sealed beam unit operating at 12V under the same ANSI standard. It fills the high beam position on 1967-1972 models.
The H5006 is a 5.75-inch round sealed beam unit, also 12V and ANSI-rated, and occupies the low beam position on 1967-1972 models. Its round form factor distinguishes it physically from the square H5001 used alongside it.
All three bulb types, H6024, H5001, and H5006, are sealed beam units. In each case the entire unit is replaced rather than an internal filament or bulb element, which is a defining characteristic of sealed beam technology.
Because the H5001 and H5006 differ in both shape and function, the two unit types used on 1967-1972 models are not interchangeable with each other, despite sharing the same voltage rating and ANSI classification framework.
The H5001 and H5006 units used on 1967-1972 models are also not interchangeable with the H6024 used on 1973-1978 models, as the physical size and housing format differ across all three part numbers.