Ford Mustang II Map Light Bulb Size

Additional Notes

• The Ford Mustang II map light specifications span the 1974-1978 model years, with three distinct bulb sizes used across that period: 1816, 212-2, and 214-2.
• The 1816 bulb is a miniature wedge type in a T3.25 form factor, rated at 12V and 4W. The T3.25 designation refers to the bulb's tubular shape, with the numeric portion indicating its width in eighths of an inch.
• The 212-2 and 214-2 are both festoon bulbs with a 41mm length and an SV8.5 base, each rated at 12V and 12W. A festoon bulb is a cylindrical lamp that mounts by pressing its end caps into spring clips rather than using a socket.
• All three bulb types conform to ANSI standards applicable in both the United States and Canada.
• The 1816 draws only 4W, while the 212-2 and 214-2 each draw 12W, meaning the map light in years fitted with festoon bulbs operates at three times the wattage of years fitted with the wedge type.
• The 212-2 and 214-2 share identical physical and electrical specifications, including the 41mm festoon length, SV8.5 base, 12V operating voltage, and 12W power rating. Despite these similarities, they carry different part numbers and are listed as separate fitments in the specifications.
• Because the 212-2 and 214-2 are catalogued as distinct bulbs for different model years, substituting one for the other is not confirmed by the specifications, even though their listed attributes are the same.
• The 1816 wedge bulb and the 212-2 or 214-2 festoon bulbs are physically and electrically incompatible with one another, as they differ in base type, form factor, and wattage.
• The 1974 and 1977 Ford Mustang II share the 212-2 fitment, while the 1975 and 1978 models share the 1816 fitment, indicating the map light specification changed multiple times across the production run.
• The SV8.5 base designation on the festoon bulbs refers to a single-contact end-cap style with an 8.5mm cap width, a standard used across many automotive interior lighting applications.