The Triumph Thunderbird high beam and low beam headlight bulbs both utilize a 9003 size. Replacement bulb specifications for the Thunderbird span from 1995 to 2014 in the chart.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Triumph Thunderbird uses the 9003 bulb size for both high beam and low beam headlights across all listed model years from 1995-2004 and 2010-2014.
The 9003 is an ANSI-standardized halogen bulb recognized in the United States and Canada, operating on a 12-volt electrical system with a dual-filament design rated at 60 watts for high beam and 55 watts for low beam.
The dual-filament construction of the 9003 allows a single bulb to serve both the high beam and low beam functions, which is reflected in the Triumph Thunderbird's identical bulb specification across both headlight positions.
The 9003 uses a P43t base, a bayonet-style mount with a 43mm collar, which physically determines fitment and is not interchangeable with single-filament bases such as the H1 or H7 without modification.
The 9003 is functionally equivalent to the HB2 designation used in international markets and the H4 bulb common in European standards, as all three share the same dual-filament halogen design and P43t base.
Because the same 9003 specification applies to both beam positions, a single replacement bulb type services the entire headlight assembly on the Triumph Thunderbird across all listed years.