The Lincoln Mark LT brake light requires a 3457 bulb size for proper installation and function within the rear lighting assembly. Data for the specific component covers the range from 2006 to 2008.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Lincoln Mark LT uses two distinct bulb types across its brake lighting system for the 2006-2008 model years: the 3457 for the standard brake lights and the 921 for the center high mount stop light.
The 3457 is a dual-filament bulb, meaning it serves two separate lighting functions within a single unit. In the context of brake lighting, this allows one filament to handle the brake signal and the other to handle a secondary function such as running lights.
The 3457 operates at 12 volts with a wattage rating of 27W/7W, where the higher wattage corresponds to the brighter filament and the lower wattage to the secondary filament.
The 3457 follows the T25 wedge form factor and conforms to ANSI standards applicable in both the United States and Canada.
The 921 is a single-filament wedge bulb rated at 12 volts and 16 watts, dedicated solely to the center high mount stop light function on the Lincoln Mark LT.
The 921 follows the T15 wedge form factor and also conforms to ANSI standards for the US and Canadian markets.
The T25 and T15 designations refer to the physical size of the wedge base, with T25 being larger than T15. These two bulb types are not interchangeable with each other due to differing base sizes and filament configurations.
The dual-filament design of the 3457 is a fitment-critical characteristic. Substituting a single-filament bulb in a socket requiring the 3457 would result in the loss of one lighting function.