The Dodge St. Regis uses H4651 bulb size for high beam headlight and H4652 bulb size for low beam headlight applications. The replacement chart covers vehicle production years spanning 1979 to 1981.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Dodge St. Regis uses the H4651 bulb size for the high beam headlight across the 1979-1981 model years.
The low beam headlight position across the same model years takes the H4652, a variant of the H4651 within the same sealed beam family.
Both the H4651 and H4652 are ANSI-standardized sealed beam units recognized in the United States and Canada, meaning they conform to a regulated specification rather than a proprietary manufacturer design.
The H4651 and H4652 are 4x6-inch rectangular sealed beam units, a form factor that houses the filament, reflector, and lens as a single fused assembly.
Because both units are sealed beams, the entire assembly is replaced when the light fails rather than an internal bulb being swapped out independently.
Both units operate on a 12-volt electrical system, which is standard for passenger vehicles of this type.
Although the H4651 and H4652 share the same physical 4x6-inch rectangular form and voltage rating, they are not interchangeable between positions, as each is designed for a distinct beam pattern, high or low.