The Mercury Montego side marker requires a 194NA bulb size for proper installation and function within the lighting assembly. Data for 194NA bulbs covers the period from 2005 through 2007.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The 194 bulb is the most frequently specified size across the Mercury Montego's side marker positions, appearing in both front and rear applications across multiple model years from 1970-1976.
The 194 is a T10 miniature wedge bulb rated at 12V and 3.78W, conforming to ANSI standards recognized in both the United States and Canada.
The 194NA shares the same T10 wedge form factor, voltage, and wattage as the standard 194 but incorporates natural amber glass, which produces the amber color through the glass itself rather than through a colored lens or housing.
The Mercury Montego (2005-2007) front side marker position calls for the 194NA specifically, meaning the amber tint is built into the bulb rather than provided by an external lens on those model years.
Substituting a standard 194 for a 194NA, or vice versa, would affect the color output of the marker light, since the amber property of the 194NA is integral to the glass envelope.
The 1971 Mercury Montego is the only model year in these specifications to use the 161 bulb in both front and rear side marker positions, and the rear side marker for 1974 and 1976 are not listed among the rear specifications, while 1974 and 1976 appear only in the front.
The 161 is also a T10 miniature wedge bulb and is physically compatible with the same socket type as the 194, but it operates at a significantly lower wattage of 1W at 12V, making the two bulbs electrically distinct despite their shared base type.
The 1969 Mercury Montego front side marker uses the 1034NA, a dual-filament bulb with a BAY15d bayonet base, which is a fundamentally different socket type from the T10 wedge used in all other listed positions.
The 1034NA is a natural amber variant of the 1157 bulb family, rated at 12V with a 21/5W dual-filament configuration, meaning it carries two separate filaments serving different circuit functions.
Because the 1034NA uses a BAY15d bayonet base, it is not interchangeable with any of the T10 wedge-base bulbs listed elsewhere in these specifications, regardless of voltage similarity.