Ford Thunderbird Dome Light Bulb Size

Additional Notes

• The Ford Thunderbird dome light specifications span from 1955 to 2005, with nine distinct bulb types used across that period: the 211-2, 912, 906, 561, 212-2, 1003, 1816, 1004, and 63.
• The 906 is a T10 miniature wedge bulb rated at 12V and 8W, making it the lowest-wattage wedge type in these specifications. It is used across multiple non-consecutive model years between 1980 and 1994.
• The 912 is a T15 wedge bulb rated at 12V and 12W and is described as a variant of the 921. It shares the same voltage and wattage as the 211-2 and 212-2 festoon types, though the base design is entirely different and the types are not interchangeable.
• The 211-2 and 212-2 are both 41mm festoon bulbs with an SV8.5 base, rated at 12V and 12W. Despite their near-identical specifications, they carry separate ANSI designations, and substitution between them warrants verification of fitment before use.
• The 561 is a 44mm festoon bulb rated at 12V and 12W. Its end-cap contact design distinguishes it physically from the SV8.5-based 211-2 and 212-2, meaning the three festoon types in these specifications are not directly interchangeable despite sharing the same voltage and wattage.
• The 1003 is a single-filament bulb with a BA15s bayonet base, rated at 12V and 21W. It is the highest-wattage bulb in these specifications and was used in the Ford Thunderbird dome light from 1957 through 1966, with the exception of 1967-1968.
• The 1816 is a T3.25 miniature wedge bulb rated at 12V and 4W, used for the 1967-1968 model years. At 4W, it draws considerably less power than the 1003 it replaced and the 1003 that followed it in 1969.
• The 1004, used on the 1959 model year, is a dual-filament bulb with a BAY15d bayonet base rated at 12V and 21/5W. It is described as a variant of the 1157 and is the only dual-filament bulb in these specifications. Its BAY15d base is offset-pin, which prevents it from being seated in a BA15s single-filament socket.
• The 63 bulb, used on the 1955 Ford Thunderbird, carries a BA9s base and is rated at just 12V and 0.63W. This output is substantially lower than every other bulb type in these specifications, reflecting the modest interior lighting standards of that era.
• Wedge-base bulbs such as the 906 and 912 are retained by socket friction alone, while bayonet-base bulbs such as the 1003 and 1004 require a twist-lock installation. These differing retention mechanisms mean that bulb types cannot be substituted across base categories regardless of voltage or wattage compatibility.