Mercury Park Lane Map Light Bulb Size

The Mercury Park Lane map light requires bulb sizes 1816, 631, and 1895 depending on the specific application. Data for the bulb sizes covers the range from 1964 to 1968.

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
1968	1816
1967	631
1966	1816
1964-1965	1895

Bulb Specifications

Description	Bulb Size
ANSI standard (US & Canada). Miniature wedge bulb (T3.25). 12V, 4W.	1816
ANSI standard (US & Canada). Single-filament bulb with BA15s bayonet base. Variant of 1156. 12V, 21W.	631
ANSI standard (US & Canada). Miniature wedge bulb (T5). 12V, 0.9W.	1895

Other Locations

Additional Notes

The Mercury Park Lane map light specifications span model years 1964 through 1968, with three distinct bulb types used across that five-year period: the 1816, the 631, and the 1895.
The 1895 bulb is a miniature wedge type rated at T5, operating at 12V and 0.9W, and it was the specified map light bulb for the Mercury Park Lane in 1964 and 1965.
The T5 designation on the 1895 refers to a tubular bulb form factor measured in eighths of an inch, making it one of the smaller miniature wedge bulbs in common automotive use.
The 1816 bulb is also a miniature wedge type, designated T3.25, and operates at 12V with a 4W output, representing a notably higher wattage than the 1895 it effectively replaced in the Park Lane's map light position.
The 1816 was specified for the Mercury Park Lane in 1966 and again in 1968, with a different bulb type appearing in the intervening 1967 model year.
The 631 bulb, specified exclusively for the 1967 Mercury Park Lane, is a single-filament bulb with a BA15s bayonet base and is rated at 12V and 21W, making it substantially more powerful than either the 1816 or the 1895.
The BA15s bayonet base of the 631 is physically incompatible with the wedge-style sockets used by the 1816 and 1895, meaning these bulb types are not interchangeable despite sharing the same 12V operating voltage.
The 631 is noted as a variant of the 1156 bulb, a widely used single-filament automotive bulb, though the 631 carries its own distinct ANSI designation and specification.
All three bulb types conform to ANSI standards applicable in both the United States and Canada, indicating standardized electrical and physical specifications across that market region.
The shift from the low-wattage 1895 in 1964-1965 to the higher-wattage 1816 in 1966, and then to the significantly higher-wattage 631 in 1967, reflects meaningful variation in the map light circuit design across these model years, and substituting one bulb type for another risks electrical incompatibility or socket mismatch.