The Ford Fusion brake light uses 921, 7443, and 4157 bulb sizes depending on the specific version of the vehicle. Available information covers a span of time starting in 2006 and ending in 2018.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Ford Fusion brake light specifications reference three distinct bulb sizes across the model's production years: 921, 7443, and 4157, all of which conform to ANSI standards recognized in both the United States and Canada.
The 921 is a single-filament wedge bulb rated at 12V and 16W, classified under the T15 form factor. Its single-filament design means it serves one lighting function at a time, making it suited for dedicated stop light or center high mount stop light applications.
The 7443 is a dual-filament wedge bulb in the T20 form factor, rated at 12V with filaments drawing 21W and 5W respectively. The dual-filament construction allows one bulb to serve both a high-intensity brake function and a lower-intensity running light function simultaneously.
The 4157 is also a dual-filament wedge bulb, housed in the larger T25 form factor and rated at 12V with filaments drawing 27W and 7W. Its higher wattage output distinguishes it from the 7443, and the two are not interchangeable despite sharing a dual-filament design.
The Ford Fusion (2006-2009) uses the 4157 bulb for the brake light position, while the 2010-2012 model years use the 7443. These two bulbs occupy different physical form factors (T25 versus T20), which prevents cross-year substitution.
The 2017-2018 Ford Fusion uses the 921 bulb for the brake light position, the same single-filament T15 type used across all listed years for the center high mount stop light.
The center high mount stop light on the Ford Fusion uses the 921 bulb across all listed years from 2006-2012, regardless of which bulb type is specified for the main brake light position in those same years.
Because the main brake light and center high mount stop light positions on the 2006-2012 Fusion use different bulb types, the two positions are not served by the same bulb, and substitution between them is not supported by the specifications.