The Autocar C / DC headlight bulb size specifications include H4651 for high beam and H4652 or H4656 for low beam applications, with each bulb size designated for specific lighting functions. The replacement chart covers 1981 through 1986 production years and documents the corresponding bulb size requirements across this 6-year span.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Autocar C / DC uses the H4651 sealed beam unit for high beam headlights across all listed model years, 1981-1986, without variation.
The low beam headlight position shows a split between two sealed beam types: the H4656 is specified for 1981-1984, while the H4652 takes over for 1985-1986.
All three bulb types present in these specifications, the H4651, H4652, and H4656, are 4x6-inch rectangular sealed beam units operating at 12V and conforming to ANSI standards recognized in both the United States and Canada.
The sealed beam construction of these units means the lens, reflector, and filament are fused into a single glass assembly. When the filament fails, the entire unit requires replacement rather than an internal bulb swap.
The H4652 is classified as a variant of the H4651. Despite this relationship, the two types are assigned to different lighting functions, with the H4651 designated for high beam and the H4652 for low beam, and they are not listed as interchangeable within these specifications.
The H4656 and H4652 occupy the same low beam position across different year ranges on the Autocar C / DC, but they carry distinct ANSI designations, which reflects differences in beam pattern or light output rather than physical form factor alone.