The Ford Explorer Sport Trac side marker utilizes 194 and 3157NA bulb sizes for the lighting components. Data for the specific bulb requirements covers the range from 2001 through 2010.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Ford Explorer Sport Trac uses two distinct bulb types across its side marker positions: the 194 and the 3157NA, both of which conform to ANSI standards recognized in the United States and Canada.
The 194 is a miniature wedge bulb in the T10 form factor, rated at 12V and 3.78W, placing it among the lower-wattage bulbs commonly found in marker and courtesy lighting applications.
The 3157NA is a dual-filament wedge bulb in the T25 form factor, rated at 12V with a 27W/7W output, meaning it carries separate wattage ratings for its two filaments, typically corresponding to a brighter active state and a dimmer running state.
The natural amber glass of the 3157NA produces a colored output directly from the bulb itself, rather than relying on a tinted lens to achieve the amber appearance required for side marker functions.
The front side marker on the Ford Explorer Sport Trac (2007-2010) uses the 194 bulb, while the same vehicle in model years 2001-2005 uses the 3157NA for that same position.
This difference in front side marker bulb type between the two production periods indicates a hardware change between generations, and the two bulb types are not interchangeable due to differences in form factor, filament count, and wattage.
The rear side marker position on the Explorer Sport Trac is specified only for 2007-2010, all of which use the 194 bulb.
The T10 and T25 designations refer to the tubular wedge base classifications of each bulb, with T25 being physically larger than T10, which further confirms that sockets designed for one will not accept the other.
The dual-filament nature of the 3157NA distinguishes it functionally from the single-filament 194, as a dual-filament bulb is capable of serving combined marker and turn signal roles within a single housing.
Both bulb types operate on a 12V electrical system, consistent with standard automotive voltage across the Explorer Sport Trac model range covered in these specifications.