GMC K15 high beam headlight bulbs use H6024 or H5001 size, while low beam headlight bulbs use H6024 or H5006 size. The replacement chart covers 1966 to 1978 vehicle 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 GMC K15 headlight bulb specifications cover the 1966-1978 model years, with two distinct sealed beam configurations appearing across that span depending on the year of manufacture.
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. On the GMC K15, it serves as both the high beam and low beam headlight for the 1973-1978 model years, meaning a single bulb type handles both functions in a dual-beam arrangement.
Sealed beam units such as the H6024, H5001, and H5006 are not serviceable in the conventional sense. When a sealed beam fails, the entire unit requires replacement rather than an internal filament or capsule.
The 1966-1972 model years use a split configuration, with the H5001 designated for high beam duty and the H5006 designated for low beam duty. These are physically distinct units and are not interchangeable with each other.
The H5001 is a 4-inch square sealed beam unit at 12V, while the H5006 is a 5.75-inch round sealed beam unit also at 12V. Their differing shapes and sizes make cross-substitution between the two physically incompatible.
The transition from the H5001/H5006 pairing to the H6024 occurred between the 1972 and 1973 model years, representing a shift from a four-lamp system using separate high and low beam units to a two-lamp system using a single dual-beam unit per side.
All three bulb types in these specifications, H6024, H5001, and H5006, operate on a 12V electrical system and share ANSI standardization, which means they conform to the same regulatory framework despite their physical differences.
The H6024 used on the 1973-1978 K15 is not a suitable replacement for either the H5001 or H5006 used on the 1966-1972 K15, as the units differ in shape, size, and beam function design.