White/GMC WIA Headlight Bulb Size

The White/GMC WIA headlight bulb uses 9004 and H6024 sizes for both high and low beam applications. A replacement chart documents bulb specifications across 1988 to 1995 production years.

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
1988-1995	9004 (With Composite Headlamps)	HB1	Check Price
1988-1995	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
1988-1995	9004 (With Composite Headlamps)	HB1	Check Price
1988-1995	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 WIA covers model years 1988-1995 in these specifications, and across all those years, the high beam and low beam headlight positions share identical bulb requirements, with fitment determined solely by headlamp system type rather than by year or beam function.
Two mutually exclusive headlamp systems are documented for the WIA: composite headlamps and sealed beam headlamps. These systems are not interchangeable, and the correct bulb type depends entirely on which system is installed on a given vehicle.
The 9004 is a dual-filament halogen bulb operating at 12V with a P29t base, rated at 65W on high beam and 45W on low beam. Its dual-filament design allows a single bulb to serve both beam functions within a composite headlamp housing.
Because the 9004 handles both high and low beam output through separate filaments, composite-equipped WIA vehicles across 1988-1995 use the same bulb part number for both beam positions, which is a direct result of the dual-filament construction.
The H6024 is a 7-inch round sealed beam unit conforming to ANSI standards for the US and Canadian markets. Unlike the 9004, it is not a replaceable bulb; the entire lens, reflector, and filament assembly is replaced as one unit.
Both the 9004 and H6024 conform to ANSI standards applicable in the US and Canada, meaning both types meet the same regional regulatory framework despite differing significantly in construction and replacement procedure.
The H6024 sealed beam unit carries a 12V rating, consistent with standard automotive electrical systems, though no wattage breakdown by beam function is specified for it in the provided data, unlike the explicit 65W/45W figures given for the 9004.
Substituting an H6024 sealed beam unit with a 9004 bulb, or vice versa, is not supported by these specifications, as each bulb type corresponds to a distinct and incompatible headlamp housing design on the WIA.