The Triumph Thunderbird LT high beam and low beam headlight bulbs both utilize a 9003 bulb size. The replacement chart covers vehicle production spanning 2014 to 2017.
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 specified across all listed model years of the Triumph Thunderbird LT, covering both high beam and low beam headlight positions.
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.
Operating voltage for the 9003 is 12V, consistent with standard 12-volt automotive electrical systems.
The 9003 uses a P43t base, which is a bayonet-style mount with a 43mm flange. This base type determines physical socket compatibility and is not interchangeable with other base configurations.
The 9003 designation follows the ANSI standard used in the United States and Canada. It is electrically equivalent to the European H4 bulb but differs in base orientation, making the two types physically non-interchangeable in most housings.
Because the 9003 serves both the high beam and low beam functions in the Triumph Thunderbird LT for the years 2014, 2016, and 2017, each headlight housing requires only one bulb per side rather than separate bulbs for each beam function.