White/GMC WG Headlight Bulb Size

Additional Notes

• The White/GMC WG carried two distinct headlamp system types across the 1990-1995 model years, each requiring a different bulb or unit: composite headlamps used the 9004 bulb, while sealed beam headlamps used the H6024 unit.
• The 9004 is a dual-filament halogen bulb operating at 12V with a high-beam filament rated at 65W and a low-beam filament rated at 45W, fitted with a P29t base. Its dual-filament design allows a single bulb to serve both the high beam and low beam functions.
• The H6024 is a 7-inch round sealed beam unit rated at 12V. Unlike the 9004, it is not a replaceable bulb; the entire lens, reflector, and filament assembly is replaced as one unit when the light fails.
• Because the 9004 handles both high and low beam functions through separate filaments within one housing, the same bulb size is listed for both the High Beam Headlight and Low Beam Headlight positions on WG models equipped with composite headlamps.
• The same pattern applies to sealed beam configurations, where the H6024 unit is listed identically for both the high beam and low beam positions, reflecting the nature of sealed beam technology in which beam function is determined by the unit's internal filament arrangement.
• Both the 9004 and H6024 conform to ANSI standards recognized in the United States and Canada, indicating standardized performance and fitment specifications within those markets.
• The 9004 bulb uses a P29t base, which is a specific connector type. Substituting a bulb with a different base type would result in an incompatible fit, even if the bulb's wattage or voltage ratings were otherwise similar.
• The H6024 sealed beam unit and the 9004 halogen bulb are not interchangeable, as they belong to fundamentally different headlamp system designs. Correct fitment depends entirely on whether the WG vehicle in question was built with composite or sealed beam headlamps.