The White/GMC ACM high beam and low beam headlight bulb sizes include 9004, H6054, and H6024 options for this vehicle model. The replacement chart covers 1988 through 1992 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 White/GMC ACM (1988-1992) used two distinct headlamp system types across its production run: composite headlamps and sealed beam headlamps. Each system required a different bulb or unit, and the two types are not interchangeable with one another.
The 9004 is a dual-filament halogen bulb operating at 12V, with a high beam output of 65W and a low beam output of 45W. It uses a P29t base and meets ANSI standards for the US and Canadian markets. A single 9004 bulb serves both the high beam and low beam functions in composite headlamp-equipped ACM vehicles.
The H6054 is a 5x7-inch rectangular sealed beam unit rated at 12V. It is not a replaceable bulb in the conventional sense; the entire unit is replaced when the light fails. It also meets ANSI standards for the US and Canadian markets.
The H6024 is a 7-inch round sealed beam unit, also rated at 12V and covered under the same ANSI standards. Like the H6054, the entire unit is replaced rather than an internal bulb. The H6024 differs physically from the H6054 and the two are not substitutes for one another.
ACM vehicles from 1988-1989 and 1991-1992 equipped with sealed beam headlamps used the H6054 rectangular unit. The 1990 model year with sealed beam headlamps used the H6024 round unit instead, making 1990 sealed beam fitment distinct from the surrounding years.
Because the H6054 and H6024 are physically different sealed beam units, a sealed beam ACM from 1990 requires a different replacement unit than sealed beam ACMs from other years in the 1988-1992 range.
The 9004 bulb was consistent across all model years from 1988-1992 for composite headlamp-equipped ACM vehicles, applying equally to both high beam and low beam positions throughout that span.
The sealed beam units (H6054 and H6024) also served dual high and low beam functions on the ACM, as the specifications list them under both the high beam and low beam sub-parts for their respective years.