The Buell S3T Thunderbolt uses a 9003 bulb size for both high beam and low beam headlight applications. The replacement chart covers vehicle production spanning 1997 to 2002 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 9003 bulb is the sole bulb type listed across all headlight positions in the Buell S3T Thunderbolt specifications, covering both high beam and low beam functions for the 1997, 1999, 2000, and 2002 model years.
The 9003 is a dual-filament halogen bulb, meaning a single bulb unit contains two separate filaments: one rated at 60W for high beam output and one rated at 55W for low beam output.
The 9003 operates on a 12V electrical system and uses a P43t base, which is a bayonet-style mount with a 43mm flange width.
The 9003 designation follows ANSI standards as applied in the United States and Canada. It is functionally equivalent to the H4 bulb used under international IEC/ECE standards, though the designations originate from different standardization bodies.
Because the 9003 and H4 share the same physical base and filament configuration, they are widely regarded as interchangeable in practice, though the designations are technically distinct.
The Buell S3T Thunderbolt uses the same 9003 bulb for both the high beam and low beam headlight positions, indicating the vehicle relies on a single dual-filament unit rather than separate bulbs for each function.