The Autocar DK 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 vehicle 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 Autocar DK uses H4651 sealed beam units for the high beam headlight across all listed model years, 1983-1988, with no variation in that position throughout the entire span.
The H4651, H4652, and H4656 are all ANSI-standardized 4x6-inch rectangular sealed beam units operating at 12V, meaning the lens, reflector, and filament are fused into a single assembly that is replaced as one complete unit rather than by swapping an internal bulb.
The H4652 is a variant of the H4651 within the same 4x6-inch rectangular sealed beam family, though the two are distinct part numbers and are not listed as interchangeable in these specifications.
The low beam position on the Autocar DK shows a split between two sealed beam types: the H4656 is specified for 1983 and 1988, while the H4652 is specified for 1984-1987.
Because the high beam and low beam positions on the Autocar DK use different sealed beam part numbers, H4651 and H4656 or H4652 respectively, the two positions are not cross-compatible despite sharing the same physical 4x6-inch rectangular form factor.
All three sealed beam types in these specifications conform to ANSI standards recognized in both the United States and Canada, placing them within a regulated dimensional and performance framework common to North American vehicle lighting.