The Autocar DS high beam headlight uses an H4651 bulb size, while low beam headlights use H4656 or H4652 bulb sizes. The replacement chart covers 1983 through 1988 production years with corresponding bulb size specifications.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The H4651, H4652, and H4656 are all ANSI-standardized sealed beam units used across the Autocar DS headlight system. Each operates at 12V and is housed in a 4x6-inch rectangular sealed beam format, meaning the lens, reflector, and filament are fused into a single non-serviceable assembly. When the filament fails, the entire unit requires replacement rather than a bulb swap.
The H4652 is a variant of the H4651. Both share the same 4x6-inch rectangular sealed beam construction and 12V rating, though they are not the same part and serve different functions within the headlight system.
The high beam position on the Autocar DS uses the H4651 across all model years from 1983-1988, making it the most consistent fitment in these specifications.
The low beam position shows a split fitment across the 1983-1988 range. The H4652 is fitted for 1983 and 1985-1987, while the H4656 appears in 1984 and 1988. These two sealed beam types are distinct parts and are not interchangeable with each other despite sharing the same physical housing size.
The ANSI standardization of the H4651, H4652, and H4656 means these sealed beam units conform to a regulated specification recognized in both the United States and Canada, governing the physical form factor and electrical interface of the assembly.
Because the H4651 and H4652 share a variant relationship, the physical housing of both units is the same 4x6-inch rectangular sealed beam, but their beam patterns and filament configurations differ, which is why they occupy separate positions in the headlight system rather than being used interchangeably.