Lincoln Mark III Map Light Bulb Size

The Lincoln Mark III map light requires bulb sizes 194, 212-2, or 631 depending on the specific application. Data for the listed components covers the period from 1968 to 1971.

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
1971	194
1969-1970	212-2
1968	631

Bulb Specifications

Description	Bulb Size
ANSI standard (US & Canada). Miniature wedge bulb (T10). 12V, 3.78W.	194
ANSI standard (US & Canada). Festoon bulb, 41mm length, SV8.5 base. 12V, 12W.	212-2
ANSI standard (US & Canada). Single-filament bulb with BA15s bayonet base. Variant of 1156. 12V, 21W.	631

Other Locations

Additional Notes

The Lincoln Mark III map light draws from three distinct bulb types across its 1968-1971 production run: the 194, 212-2, and 631.
All three bulb types conform to ANSI standards recognized in both the United States and Canada.
The 194 is a T10 miniature wedge bulb rated at 12V and 3.78W, making it the lowest-wattage unit among the three types specified for this vehicle.
The 212-2 is a festoon bulb with an SV8.5 base and a 41mm length, rated at 12V and 12W. Its festoon form factor means it is held in place by contact pressure at each end rather than by a socket or bayonet mount.
The 631 carries a BA15s bayonet base and is rated at 12V and 21W, making it the highest-wattage bulb in this specification set. It is a single-filament variant related to the 1156 bulb family.
The 212-2 festoon bulb was used in the Lincoln Mark III for the 1969-1970 model years.
The 194 wedge and 212-2 festoon types are not interchangeable due to their fundamentally different base designs. A wedge base seats into a slotted socket, while the SV8.5 festoon base relies on end-cap contact.
The 631 and 194 are likewise incompatible with each other, as the BA15s bayonet base requires a twist-lock socket that neither the wedge nor the festoon format uses.
The 1968 Lincoln Mark III uses the 631 bulb, which at 21W draws notably more power than the 194 fitted to the 1971 model year.