The GMC C3500 brake light utilizes 1157, 2057, and 3057 bulb sizes depending on the specific version of the vehicle. Available data for the lighting components covers the range from 1979 through 2000.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The GMC C3500 brake light circuit relies on three dual-filament bulb types across its model range: the 3057, 1157, and 2057. Each type carries two separate wattage ratings because one filament serves the running light function while the higher-wattage filament activates under braking.
The 3057 is the most frequently specified brake bulb for the GMC C3500, covering model years 1990-1995, 1998-2000. It follows the ANSI standard and uses a T25 wedge base rated at 12V with a 27W brake filament and a 7W running filament.
The 1157 appears in 1979-1982, 1994, and 1996-1997. It uses a BAY15d bayonet base and operates at 12V with a 21W brake filament and a 5W running filament. The bayonet base is physically distinct from the wedge base of the 3057, making the two types non-interchangeable without a socket adapter.
The 2057 is specified for 1983-1986 and 1988-1989. Like the 1157, it uses a BAY15d bayonet base, but its filaments are rated at 26.9W and 8W respectively, placing its output closer to the 3057 despite sharing the same base type as the 1157.
Because the 2057 and 1157 share the BAY15d bayonet base, the 2057 can physically seat in a socket designed for the 1157. However, the two bulbs carry different wattage ratings, and substitution affects light output.
The 3057 uses a T25 wedge base, while the 1157 and 2057 use a BAY15d bayonet base. These two base types are mechanically incompatible, so a socket built for one will not accept the other without modification.
The center high mount stop light on the GMC C3500 uses single-filament wedge bulbs rather than the dual-filament types found in the main brake circuit. This reflects the dedicated stop-only function of that lamp position.
The 921 is the predominant center high mount stop light bulb, specified for 1993-1997 and 1999-2000. It is a T15 wedge bulb rated at 12V and 16W.
The 912 is specified for the center high mount stop light in 1998 only. It shares the T15 wedge form factor with the 921 but is rated at 12W rather than 16W, making it a lower-output variant of the same base type.
All bulb types listed for the GMC C3500 brake system conform to ANSI standards applicable in both the United States and Canada, indicating consistent regulatory compliance across the full production range covered by these specifications.