Mercury Montego Map Light Bulb Size

The Mercury Montego map light uses bulb sizes 105, 578, 1003, 1816, and 212-2. Data for the specified vehicle components covers the period from 1968 through 2007.

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
2006-2007	212-2 (Front)
2006-2007	578 (Rear)
2005	212-2
1976	105
1972-1975	1003
1968-1970	1816

Bulb Specifications

Description	Bulb Size
ANSI standard (US & Canada). Festoon bulb, 41mm length, SV8.5 base. 12V, 12W.	212-2
ANSI standard (US & Canada). Festoon bulb, 41mm length, end-cap contacts. 12V, 12W.	578
ANSI standard (US & Canada). Single-filament bulb with BA15s bayonet base. Variant of 1156. 12V, 13W.	105
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 Mercury Montego map light specifications span two distinct production eras: the modern generation from 2005-2007 and the classic generation from 1968-1976, with each era using entirely different bulb types.
The 212-2 is the most frequently specified bulb across the modern Montego lineup, covering the front map light position for 2005-2007. It is a festoon-style bulb with an SV8.5 base, rated at 12V and 12W, conforming to ANSI standards for the US and Canadian markets.
The 578 bulb shares the same 41mm festoon form factor and 12V/12W electrical rating as the 212-2, but uses end-cap contacts rather than an SV8.5 base. This distinction makes the two bulbs non-interchangeable despite their otherwise identical physical size and power draw.
For 2006-2007 Mercury Montego models, the front and rear map light positions require different bulb types, with the 212-2 assigned to the front and the 578 assigned to the rear.
The 1003 bulb is specified across four consecutive model years, 1972-1975, making it the most consistently used bulb in the classic-era Montego map light data. It is a single-filament bulb with a BA15s bayonet base, rated at 12V and 21W.
At 21W, the 1003 bulb draws significantly more power than any other bulb type in these specifications, including the 12W festoon bulbs used in the modern generation and the 4W 1816 used in the late 1960s models.
The 1816 is a miniature wedge bulb of the T3.25 type, rated at 12V and 4W. It is specified for the Mercury Montego across three model years, 1968-1970, and represents the lowest wattage among all bulb types in these specifications.
The 105 bulb, specified for the 1976 Montego, shares the BA15s bayonet base with the 1003 and is noted as a variant of the 1156. However, at 13W it draws less power than the 1003, and the two are not confirmed as interchangeable within these specifications.
All bulb types listed across the full Montego map light specifications conform to ANSI standards applicable to both the United States and Canada.
The 2005 Montego specification lists only a single map light bulb, the 212-2, without a separate rear position entry, whereas the 2006 and 2007 model years each carry two distinct position-specific entries.