White/GMC WCS Headlight Bulb Size

The White/GMC WCS high beam and low beam headlight bulb size measures 9004 or H6024. The replacement chart covers 1988 to 1991 production years with bulb size specifications.

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

High Beam Headlight

If US Type and EU Type show the same value, a direct cross-reference for this bulb is not available or the data is insufficient.

Years	US Type	EU Type	Shop
1988-1991	9004 (With Composite Headlamps)	HB1	Check Price
1988-1991	H6024 (With Sealed Beam Headlamps)	H6024	Check Price

Low Beam Headlight

If US Type and EU Type show the same value, a direct cross-reference for this bulb is not available or the data is insufficient.

Years	US Type	EU Type	Shop
1988-1991	9004 (With Composite Headlamps)	HB1	Check Price
1988-1991	H6024 (With Sealed Beam Headlamps)	H6024	Check Price

Bulb Specifications

Description	Type	Shop
ANSI standard (US & Canada). Dual-filament halogen bulb with P29t base. 12V, 65W/45W.	9004	Check Price
ANSI standard (US & Canada). 7-inch round sealed beam unit. Not a replaceable bulb — the entire unit is replaced. 12V.	H6024	Check Price

Other Locations

Additional Notes

The White/GMC WCS used two distinct headlamp system types across the 1988-1991 model years: composite headlamps and sealed beam headlamps. Each system requires a different bulb or unit, and the two are not interchangeable.
The 9004 is a dual-filament halogen bulb operating at 12V with a wattage rating of 65W on high beam and 45W on low beam. It uses a P29t base and conforms to ANSI standards applicable in both the United States and Canada.
Because the 9004 carries both high and low beam filaments within a single housing, it serves both the High Beam Headlight and Low Beam Headlight positions on WCS models equipped with composite headlamps.
The H6024 is a 7-inch round sealed beam unit rated at 12V and also conforms to ANSI standards for the United States and Canada. Unlike the 9004, the H6024 is not a replaceable bulb; the entire unit is replaced when it fails.
The H6024 similarly covers both the high beam and low beam functions on WCS models equipped with sealed beam headlamps, as reflected in its listing under both sub-parts across all four model years.
The headlamp system type present on a given vehicle determines which of the two specifications applies. Fitting a 9004 bulb to a sealed beam housing, or attempting to install an H6024 unit in a composite headlamp assembly, would constitute an incompatible substitution.