Ford Mustang II Dome Light Bulb Size

The Ford Mustang II dome light utilizes bulb size 1816 and bulb size 212-2 for interior illumination. Data for the specified components covers the range from 1974 through 1978.

The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.

Bulb Size by Year Range

Years	Bulb Size
1978	1816
1974-1977	212-2

Bulb Specifications

Description	Bulb Size
ANSI standard (US & Canada). Miniature wedge bulb (T3.25). 12V, 4W.	1816
ANSI standard (US & Canada). Festoon bulb, 41mm length, SV8.5 base. 12V, 12W.	212-2

Other Locations

Additional Notes

The Ford Mustang II dome light draws from two distinct bulb types across its production run: the 1816 and the 212-2, both conforming to ANSI standards recognized in the United States and Canada.
The 212-2 is a festoon-style bulb with an SV8.5 base and a 41mm length, operating at 12 volts and rated at 12 watts.
The 1816 is a miniature wedge bulb in a T3.25 form factor, also rated at 12 volts but drawing only 4 watts, making it significantly lower in wattage than the 212-2.
The Ford Mustang II (1974-1977) used the 212-2 festoon bulb as the specified dome light fitment across four consecutive model years.
The 1978 model year transitioned to the 1816 wedge bulb, which uses a physically different base type than the festoon-style 212-2 and is not a direct drop-in replacement for it.
The SV8.5 base on the 212-2 is a cylindrical festoon contact design, whereas the 1816 uses a wedge base that seats by friction rather than by end-cap contact, meaning the two bulbs require different socket types.
The wattage difference between the 212-2 (12W) and the 1816 (4W) reflects a substantial gap in power draw, which has implications for socket and circuit compatibility if a substitution were attempted.