Mercury Zephyr Map Light Bulb Size

The Mercury Zephyr map light requires bulb size 105, 1816, or 906 depending on the specific version of the vehicle. Data for the bulb sizes covers the range from 1978 to 1983.

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
1983	105
1980-1981	105
1979	1816
1978	906

Bulb Specifications

Description	Bulb Size
ANSI standard (US & Canada). Single-filament bulb with BA15s bayonet base. Variant of 1156. 12V, 13W.	105
ANSI standard (US & Canada). Miniature wedge bulb (T3.25). 12V, 4W.	1816
ANSI standard (US & Canada). Miniature wedge bulb (T10). 12V, 8W.	906

Other Locations

Additional Notes

The Mercury Zephyr map light specifications cover model years 1978-1983, with three distinct bulb types used across that span: the 105, 1816, and 906.
The 105 bulb is the most frequently specified type, covering the 1980, 1981, and 1983 Mercury Zephyr model years for the map light position.
The 105 is an ANSI-standard single-filament bulb rated at 12V and 13W, fitted with a BA15s bayonet base, and is classified as a variant of the more widely known 1156 bulb.
The BA15s bayonet base of the 105 bulb is a single-contact design, which is not interchangeable with dual-contact bayonet bases such as the BA15d, despite sharing the same physical shell size.
The 1979 model year uses the 1816, a T3.25 miniature wedge bulb rated at 12V and 4W, making it significantly lower in wattage than the 105 used in surrounding years.
The 1978 model year uses the 906, a T10 miniature wedge bulb rated at 12V and 8W, placing it between the 1816 and the 105 in terms of power output.
Both the 1816 and 906 use wedge bases, which are physically incompatible with the BA15s bayonet socket required by the 105 bulb.
All three bulb types carry ANSI standardization applicable to the US and Canadian markets, indicating consistent regulatory compliance across the full range of listed model years.
The wattage difference between the 906 (8W) and the 1816 (4W) means the two wedge-base bulbs, though sharing a similar base style, are not functionally equivalent substitutes for one another in a map light application.
The T10 designation of the 906 refers to a tubular bulb form with a width of approximately 10 thirty-seconds of an inch, while the T3.25 of the 1816 denotes a narrower tubular form, reflecting a physical size difference between the two wedge types.