Mercury Topaz Map Light Bulb Size

The Mercury Topaz map light requires a bulb size of 1816 for the interior lighting component. Data for the specified bulb size covers the range from 1984 to 1994.

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
1984-1994	1816

Bulb Specifications

Description	Bulb Size
ANSI standard (US & Canada). Miniature wedge bulb (T3.25). 12V, 4W.	1816

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Additional Notes

The Mercury Topaz map light uses the 1816 bulb across all listed model years, spanning 1984-1994.
The 1816 is an ANSI-standardized bulb recognized in both the United States and Canada, meaning it conforms to a defined set of electrical and physical specifications shared across manufacturers.
This bulb follows the T3.25 designation, which refers to a tubular miniature wedge form factor. The T-series numbering reflects the bulb's width in eighths of an inch, placing the T3.25 at just over 10mm wide.
The 1816 operates at 12 volts and 4 watts, consistent with low-current interior lighting applications such as map lights.
The wedge base design means the 1816 has no metal screw base or separate pins. Instead, the glass envelope itself, with its flattened base, acts as the retention mechanism within the socket.
The consistent fitment of the 1816 across the entire 1984-1994 production span of the Mercury Topaz indicates no mid-generation socket changes were made to the map light housing during that period.
Wedge-base bulbs like the 1816 are generally interchangeable with other T3.25 wedge bulbs of matching voltage and wattage, provided the physical base width is compatible with the socket.
Substituting a bulb with a higher wattage rating than 4W in this application risks exceeding the thermal tolerance of the map light housing, as interior plastic components are rated for the heat output of the original specification.