Mercury Commuter Dome Light Bulb Size

The Mercury Commuter dome light utilizes 1003 and 1816 bulb sizes for interior illumination. Available data for the specified vehicle covers the range from 1957 through 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	1003
1967	1816
1957-1966	1003

Bulb Specifications

Description	Bulb Size
ANSI standard (US & Canada). Single-filament bulb with BA15s bayonet base. 12V, 21W.	1003
ANSI standard (US & Canada). Miniature wedge bulb (T3.25). 12V, 4W.	1816

Other Locations

Additional Notes

The 1003 bulb is the dominant dome light specification for the Mercury Commuter, covering model years 1957-1966 and 1968.
The 1003 is an ANSI-standard single-filament bulb rated at 12 volts and 21 watts, fitted with a BA15s bayonet base.
A BA15s bayonet base is a single-contact bayonet mount, meaning the base has one electrical contact pin rather than two offset pins.
The 1816 bulb applies exclusively to the 1967 Mercury Commuter dome light, making it the sole model year with a different specification in this range.
The 1816 is an ANSI-standard miniature wedge bulb of the T3.25 type, rated at 12 volts and 4 watts.
The wattage difference between the two bulb types is substantial. The 1003 draws 21 watts while the 1816 draws only 4 watts, meaning the two types are not electrically equivalent.
The 1003 uses a BA15s bayonet base while the 1816 uses a wedge-style base, so the two bulbs are physically incompatible with each other's sockets.
Both the 1003 and 1816 are classified under ANSI standards applicable in the United States and Canada.